Synthesis of fluoro-substituted acrylic monomers bearing a functionalized lateral chain: Part 1. Preparation of sulfur-containing monomers

Article abstract of DOI:10.1016/S0022-1139(01)00341-4

The synthesis of sulfur-containing fluoroacrylic monomers C_mF_2m+1(CH₂)₂S(CH₂)_n OC(O)CH=CH₂ (where m=6, 8 and n=2-4, 11) is presented from a two-step procedure. The first deals with the radical addition of fluorinated mercaptans C_mF_2m+1(CH₂)₂SH onto ω-unsaturated alcohols leading to new ω-perfluorinated alcohols containing various polymethylene spacers C_mF_2m+1(CH₂)₂S(CH₂)_n OH according to the nature of the unsaturated alcohols. By-products were noted, resulting from the β-addition of the thiyl radical onto the more hindered side of the alcohol. The proportion of linear and branched isomers is discussed according to the stability of the radical intermediates. These minor products were obtained selectively from other routes to confirm their presence in the reaction media. The second step deals with the acrylation reaction that occurred either in the presence of acryloyl chloride or from a Fisher esterification. Both reactions are described and discussed taking into account the nature of the starting alcohols. The formation of thiiranium ions as intermediates in the esterification of β-sulfur-containing alcohols in acidic medium is established and the formation of regioisomers described according to this thiiranium moieties interposition.

Full text of DOI:10.1016/S0022-1139(01)00341-4

Journal of Fluorine Chemistry 108 .2001) 133±142
Synthesis of ¯uoro-substituted acrylic monomers
bearing a functionalized lateral chain
Part 1. Preparation of sulfur-containing monomers
B. Peesa,d,*, A. Cahuzacb, M. Sindta, B. Amedurib,*, J.M. Paulc,
Â
B. Boutevinb, J.L. Mieloszynskia
Á Â Â
Laboratoire de Chimie Organique Ð Syntheses et Applications Organiques, Produits et Procedes,
a
Â
Universite de Metz Ð U.F.R. Sci. F.A., Ile du Saulcy, 57012 Metz Cedex 01, France
 Â
Laboratoire de Chimie Macromoleculaire, Ecole Nationale Superieure de Chimie de Montpellier,
b
UMR 5060, 8 rue de l'Ecole Normale, 34296 Montpellier Cedex 5, France
Â
c
Ato®na, Centre de Recherches et Developpement de l'Est, B.P. 61005, 57501 Saint-Avold Cedex, France
dAto®na, CERDATO, Laboratory of Materials, 27470 SERQVIGNY, France
Received 10 July 2000; accepted 13 December 2000
Abstract
The synthesis of sulfur-containing ¯uoroacrylic monomers CmF2m‡1.CH2)2S.CH2)nOC.O)CH=CH2 .where m ˆ 6, 8 and n ˆ 2±4, 11) is
presented from a two-step procedure. The ®rst deals with the radical addition of ¯uorinated mercaptans CmF2m‡1.CH2)2SH onto o-
unsaturated alcohols leading to new o-per¯uorinated alcohols containing various polymethylene spacers CmF2m‡1.CH2)2S.CH2)nOH
according to the nature of the unsaturated alcohols. By-products were noted, resulting from the b-addition of the thiyl radical onto the more
hindered side of the alcohol. The proportion of linear and branched isomers is discussed according to the stability of the radical
intermediates. These minor products were obtained selectively from other routes to con®rm their presence in the reaction media. The
second step deals with the acrylation reaction that occurred either in the presence of acryloyl chloride or from a Fisher esteri®cation. Both
reactions are described and discussed taking into account the nature of the starting alcohols. The formation of thiiranium ions as
intermediates in the esteri®cation of b-sulfur-containing alcohols in acidic medium is established and the formation of regioisomers
described according to this thiiranium moieties interposition. # 2001 Elsevier Science B.V. All rights reserved.
Keywords: Fluorinated tails; Thiyl radicals; Thiiranium ion; Acrylic monomers; Radical addition; Fluorinated alcohols
1. Introduction
ination of polymers [30,31]. Fluorinated acrylics are of great
interest mainly for their good surface properties, and they
have been widely investigated .wettability and surface
properties [32±35], structural properties [36±40] and poly-
merization [41±47]).
Usually, ¯uoroacrylates synthesized industrially are
achieved in a three-step procedure: by ethylenation of
per¯uoroalkyl iodides, followed by a hydrolysis leading
to2-per¯uoroalkyl-ethanolandthenbyacrylationofhydroxyl
end-group.Many¯uoroacrylicmonomershavebeenachieved,
however, quite a few contain a thioether bridge [48].
The aim of the present work is the preparation of ¯uori-
nated acrylates containing a thioether function as a spacer
link between the ¯uorinated chain and the acrylic group, as
follows:
The synthesis of ¯uorinated monomers is of increasing
interest because of a wide range of applications of ¯uor-
ocarbon polymers [1±3]. Due to their low surface energy [4],
low friction coef®cient [5] and aggressive chemicals resis-
tance [6], these materials ®nd applications in many areas
such as adhesion and lubricants [7,8], biocompatibility [9],
solvent resistance [10], material coatings [11] .for textiles
[12±15], optical ®bers [16], stone [17,18], leather [19,20],
metal [21,22], wood [23] and paper [24]). Fluorinated
polymers have mainly been prepared according to two ways:
free radical polymerization of ¯uoroole®ns and polycon-
densation .polyesters [25], polyurethanes [26], polystyrenes
[27], polyacrylamides [28] or polysiloxanes [29]) or ¯uor-
* Corresponding authors. fax: ‡33-467-14-4368 .B. Ameduri);
Â
fax ‡33-387-54-73-13 .B. Pees).
0022-1139/01/$ ± see front matter # 2001 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 1 1 3 9 . 0 1 ) 0 0 3 4 1 - 4

Â
B. Pees et al. / Journal of Fluorine Chemistry 108 D2001) 133±142
134
It is well known that the homopolymers and copolymers
.0.12 mm)). Helium was used as the carrier gas, the detector
and the injector temperature were 300 and 2808C, respec-
tively. The temperature program started from 608Cand
reached 3008Cat a heating rate of 4 8Cmin À1. The GC
apparatus was connected to a Hewlett-Packard mass spectro-
meter .MS) .model 5971 A, 70 eV electron-impact ion
source).
are useful in textile treatment to allow the oil and water
repellency [49,50]. The route presented in this work is an
interesting way to achieve the synthesis of several mono-
mers .n ˆ 3±11 and m ˆ 6±8), thanks to a large range of o-
unsaturated alcohols used with different 2-per¯uoroalkyl-
ethanethiols.
2. Experimental details
2.2. Synthesis
2.1. General comments
2.2.1. Radical addition of 2-perfluoroalkyl-ethanethiol
onto o-unsaturated alcohol or allyl phenyl ether
A mixture of 1.3 equiv. of o-unsaturated adduct, 0.03
equiv. of AIBN and cyclohexane or acetonitrile was purged
with nitrogen and heated at 808Cunder nitrogen. Then, a
solution of 1 equiv. of 2-per¯uoroalkyl-ethanethiol in cyclo-
hexane or acetonitrile was added dropwise and the mixture
was re¯uxed for 4 h.
For compounds a, the reaction mixture was dried over
Na2SO4 and the solvent evaporated under vacuum. The
mixture of isomers 1a and 2a was distilled under reduced
pressure.
For compounds b, d, e, f and g, after cooling down to
room temperature, the reaction mixture was dissolved in
chloroform and dried over anhydrous Na2SO4. After eva-
poration of the solvents under vacuum, products were
recrystallized from either cyclohexane or ethanol/water
.70/30, v/v).
Acrylic acid, hydroquinone monomethyl ether .HQME),
2-per¯uorohexyl-ethanethiol, 2-per¯uorooctyl-ethanethiol,
and 1-iodo-2-per¯uorooctyl-ethane were kindly supplied
by Elf-Atochem. The last reactant was treated with a dilute
solution of Na2S2O3 prior to use while the other did not
undergo any puri®cation. Allyl alcohol, but-3-en-1-ol,
undec-10-en-1-ol, 2-chloro-ethan-1-ol, 3-chloro-propan-
1-ol, 1-mercapto-propan-1-ol, thiolactic acid, lithium
aluminum hydride, sodium, p-toluenesulfonic acid .APTS),
acryloyl chloride and triethylamine were supplied from
Aldrich and used as received, excepting for triethylamine
which was distilled over CaH2 under nitrogen. 2,20-Azobi-
sisobutyronitrile .AIBN), anhydrous sodium sulfate, sodium
hydroxide, calcium hydride, calcium chloride, sodium
hydrogen carbonate, sodium carbonate, potassium carbonate
and ammonium chloride were purchased from Fluka. A 1N
solution of hydrochloric acid was supplied from SDS.
Dichloromethane, chloroform, toluene, cyclohexane, acet-
onitrile, ethanol and tetrahydrofuran were purchased from
Carlo-Erba. Anhydrous solvents were distilled under nitro-
gen over CaCl2 for dichloromethane and over sodium for
tetrahydrofuran.
Mixture of 1a and 2a .90/10). Yield: 64%; yellow liquid;
bp 1458C/0.5 mbar.
1
Compound 1a. H NMR d .ppm): 3.73 .t, J ˆ 6:1 Hz,
OCH2); 2.74 .tt, .4JHF), JHH ˆ 8:9 Hz, SCH2CH2CF2); 2.67
3
.t, J ˆ 7:0 Hz, CH2S); 2.37 .tt, JHH ˆ 8:9 Hz, JHF
ˆ
17:8 Hz, CH2CH2CF2); 1.90 .broad s, shifted with dilution,
OH); 1.84 .tt, J ˆ 6:1 Hz, J ˆ 7:0 Hz, CH2). 13CNMR d
.ppm): 105±125 .m, 5CF2 and CF3); 60.8 .s, OCH2); 32.0 .t,
2JCF ˆ 22:0 Hz, CH2CF2); 31.8 .s, CH2S); 28.6 .s, CH2);
22.5 .t, 3JCF ˆ 4:4 Hz, SCH2CH2CF2). GC-MS m/z .%): 59
.40); 69 .12); 105 .5); 119 .5); 131 .4); 169 .2); 379 .2); 407
.100); 438 .11).
After esteri®cation the monomers were stabilized with
250 ppm of HQME.
1H, 13Cand 19F NMR spectra were obtained on a Bruker
AC-250 spectrometer using tetramethylsilane .TMS) .for 1H
and 13C) and CFCl3 .for 19F) as internal references and
CDCl3 as solvent. The letters s, d, t, q and m designate
singlet, doublet, triplet, quartet and multiplet, respectively.
The 19F NMR analysis of every compound could be
described as two types of spectra, one type for each length
of per¯uorinated group.
A
1
Compound 2a. H NMR d .ppm): 3.70 .m, CH ); 3.50
.m, CHB); 2.90 .m, CHXS); 2.74 .m, SCH2CH2CF2); 2.37
.m, CH2CF2); 1.90 .broad s, shifted with dilution, OH); 1.29
.d, JMX ˆ 6:9 Hz, CH3M). 13CNMR d .ppm): 105±125
.m, 7CF2 and CF3); 65.9 .s, OCH2); 43.7 .s, CHS); 32.4
.t, 2JCF ˆ 23:0 Hz, CH2CF2); 20.9 .m, SCH2CH2CF2); 17.7
.s, CH3). GC-MS m/z .%): 45 .30); 59 .100); 69 .25); 119
.10); 131 .8); 169 .4); 393 .12); 407 .9); 438 .32).
Tail C6F13, d .ppm): À81.2 .t, J ˆ 9:5 Hz, CF3, 3F);
À113.7 .m, CF2CH2, 2F); À122.4 .m, CF2CF2CF2CH2,
4F); À123.5 .m, C2F5CF2, 2F); À126.6 .m, CF3CF2, 2F).
Tail C8F17, d .ppm): À81.1 .t, J ˆ 9:5 Hz, CF3, 3F);
À113.6 .m, CF2CH2, 2F); À122.2 .m, CF2CF2CF2CF2CH2,
6F); À123.1 .m, C3F7CF2, 2F); À123.4 .m, C2F5CF2, 2F);
À126.5 .m, CF3CF2, 2F).
Compound 1b. Yield: 56%; white solid; 1H NMR d
3
.ppm): 3.64 .t, J ˆ 6:6 Hz, OCH2); 2.73 .tt, .4JHF), JHH
3
ˆ 8:3 Hz, SCH2CH2CF2); 2.55 .t, JHH ˆ 7:3 Hz, CH2S);
3
3
After reaction, some compounds were analyzed by gas
chromatography .GC) using a Hewlett-Packard apparatus
.model 5890 SII) equipped with an ``WCOT Fused Silica''
type column .25 m  0:25 mm, stationary phase: CPSil5CB
2.37 .tt, JHH ˆ 8:4 Hz, JHF ˆ 17:4 Hz, CH2CH2CF2);
1.56 .m, 2CH2); 1.29 .m, 7CH2 and OH). 13CNMR
.ppm): 105±125 .m, 5CF2 and CF3); 63.1 .s, OCH2); 32.8
.s, CH2S); 32.3 .s, CH2); 32.2 .t, 2JCF ˆ 22:0 Hz, CH2CF2);
d

Â
B. Pees et al. / Journal of Fluorine Chemistry 108 D2001) 133±142
135
1
28.8±29.6 .m, 7CH2); 25.7 .s, CH2); 22.6 .t, 3JCF ˆ 4:5 Hz,
Compound 2g. H NMR d .ppm): 6.89±7.32 .m, 5CH);
SCH2CH2CF2).
Mixture of 1d and 2d .90/10). Yield: 87%; white solid; mp
668C.
4.07 .m, CHA); 3.95 .m, CHB); 2.90 .m, CHXS); 2.76 .m,
3
3
SCH2CH2CF2); 2.43 .tt, JHH ˆ 8:7 Hz, JHF ˆ 17:5 Hz,
CH2CF2); 1.40 .d, JMX ˆ 7:1 Hz, CH3M).
1
Compound 1d. H NMR d .ppm): 3.78 .t, J ˆ 6:0 Hz,
3
OCH2); 2.75 .tt, .4JHF), JHH ˆ 8:5 Hz, SCH2CH2CF2);
2.2.2. Radical addition of 2-perfluoroalkyl-ethanethiol
onto vinyl acetate
A mixture of 1 equiv. of vinyl acetate, 1 equiv. of
2-per¯uorooctyl-ethanethiol, 0.03 equiv. of 2,20-azobisiso-
butyronitrile .AIBN) and cyclohexane was purged with
nitrogen and re¯uxed for 4 h.
After cooling down to room temperature, the reaction
mixture was dried over anhydrous Na2SO4 and solvent
evaporated under vacuum.
3
3
2.70 .t, JHH ˆ 7:2 Hz, CH2S); 2.39 .tt, JHH ˆ 8:5 Hz,
3JHF ˆ 17:1 Hz, CH2CH2CF2); 1.87 .tt, J ˆ 6:0 Hz,
J ˆ 7:2 Hz, CH2); 1.59 .broad s, shifted with dilution,
OH). 13CNMR d .ppm): 105±125 .m, 7CF2 and CF3);
2
61.3 .s, OCH2); 32.1 .t, JCF ˆ 22:1 Hz, CH2CF2); 31.8
3
.s, CH2S); 28.8 .s, CH2); 22.7 .t, JCF ˆ 4:2 Hz,
SCH2CH2CF2). GC-MS m/z .%): 58 .100); 69 .26); 91
.11); 119 .10); 131 .10); 169 .6); 441 .2); 475 .3); 493
.5); 538 .8).
1
Compound 1h. Yield: 89%; colorless liquid; H NMR d
Compound 2d. 1H NMR d .ppm): 3.68 .m, CHA); 3.55 .m,
.ppm): 4.25 .t, JHH ˆ 6:4 Hz, OCH2); 2.79 .m,
3
B
X
3
3
CH ); 2.92 .m, CH S); 2.79 .tt, .4JHF), JHH ˆ 8:6 Hz,
SCH2CH2CF2 and CH2S); 2.39 .tt, JHH ˆ 8:7 Hz,
3
3
SCH2CH2CF2); 2.39 .tt, JHH ˆ 8:6 Hz, JHF ˆ 17:3 Hz,
M
3JHF ˆ 17:4 Hz, CH2CH2CF2); 2.06 .s, CH3). 13CNMR d
CH2CF2); 2.05 .broad s, shifted with dilution, OH); 1.31
.ppm): 170.6 .s, C=O), 105±125 .m, 7CF2 and CF3); 63.5 .s,
2
.d, JMX ˆ 7:1 Hz, CH3 ). 13CNMR d .ppm): 105±125 .m,
OCH2); 32.5 .t, JCF ˆ 22:1 Hz, CH2CF2); 30.7 .s, CH2S);
3
7CF2 and CF3); 65.9 .s, OCH2); 43.6 .s, CHS); 32.4 .t,
2JCF ˆ 22:0 Hz, CH2CF2); 20.9 .t, 3JCF ˆ 4:5 Hz,
SCH2CH2CF2); 17.6 .s, CH3). GC-MS m/z .%): 59 .100);
61 .50); 69 .35); 119 .12); 131 .11); 169 .6); 507 .100); 538
.10).
23.0 .t, JCF ˆ 4:3 Hz, SCH2CH2CF2).
2.2.3. Esterification of 2-perfluoroalkyl-ethyl
o-hydroxy-alkyl sulfide
Method 1 .for a, b, d, e, f). Acrylic acid .1.25 equiv., 30%
solution in toluene) was added to 1 equiv. of alcohol, 0.1
equiv. of p-toluenesulfonic acid .PTSA), 250 ppm of hydro-
quinone monomethyl ether .HQME) and toluene. This
mixture was re¯uxed for 12 h under a water separator
.Dean±Stark apparatus). When the theoretical amount of
water was collected, the reaction was stopped and the
solvent was removed by distillation under vacuum. The
total product mixture was dissolved in chloroform and
treated with NaOH 10% and washed with water until pH
7±8. After drying over anhydrous Na2SO4, solvent was
distilled off in vacuum.
Mixture of 1e and 2e .95/05). Yield: 85%; white solid.
Compound 1e. 1H NMR d .ppm): 3.68 .t, 3JHH ˆ 5:8 Hz,
3
OCH2); 2.74 .tt, .4JHF), JHH ˆ 8:5 Hz, SCH2CH2CF2);
3
3
2.60 .t, JHH ˆ 6:8 Hz, CH2S); 2.37 .tt, JHH ˆ 8:5 Hz,
3JHF ˆ 17:1 Hz, CH2CH2CF2); 1.69 .m, 2CH2); 1.50 .broad
s, shifted with dilution, OH). 13CNMR d .ppm): 105±125
.m, 7CF2 and CF3); 62.3 .s, OCH2); 32.2 .t, 2JCF ˆ 22:2 Hz,
CH2); 32.1 .s, CH2); 31.5 .s, CH2); 25.7 .s, CH2); 21.6 .t,
3JCF ˆ 4:4 Hz, CH2).
Compound 2e. 1H NMR d .ppm): 3.68 .t, 3JHH ˆ 5:8 Hz,
OCH2); 3.0 .m, CHS); 2.79 .m, SCH2CH2CF2); 2.39 .m,
CH2CF2); 1.69 .m, CH2); 1.50 .broad s, shifted with dilu-
tion, OH); 1.35 .d, J ˆ 6:7 Hz, CH3). GC-MS m/z .%): 59
.100); 61 .50); 69 .35); 119 .12); 131 .11); 169 .6); 507
.100); 538 .10).
Mixture of 3a and 5a .90/10). Yield: 80%; orange liquid.
Compound 3a. 1H NMR d .ppm): 6.41 .dd, JAB ˆ 1:5 Hz,
JAX ˆ 17:3 Hz, CHA); 6.11 .dd, JAX ˆ 17:3 Hz, JBX
ˆ
10:4 Hz, CHX); 5.83 .dd, JBX ˆ 10:4 Hz, JAB ˆ 1:5 Hz,
CHB); 4.27 .t, JHH ˆ 6:2 Hz, OCH2); 2.73 .tt, .4JHF),
1
3
Compound 1f. Yield: 82%; white solid; mp 808C; H
3
3
NMR d .ppm): 3.64 .t, JHH ˆ 6:5 Hz, OCH2); 2.73 .tt,
JHH ˆ 9:0, SCH CH2CF2); 2.65 .t, JHH ˆ 7:3 Hz, C HS);
2
2
3
3
3
3
.4JHF), JHH ˆ 7:3 Hz, SCH2CH2CF2); 2.55 .t, JHH
ˆ
2.37 .tt, JHH ˆ 9:0 Hz, JHF ˆ 18:2 Hz, CH2CH2CF2);
3 3
3
7:3 Hz, CH2S); 2.37 .tt, JHH ˆ 7:3 Hz, JHF ˆ 14:6 Hz,
CH2CH2CF2); 1.57 .m, 2CH2); 1.29 .m, 7CH2 and OH).
13CNMR d .ppm): 105±125 .m, 7CF2 and CF3); 63.0 .s,
OCH2); 32.8 .s, CH2S); 32.3 .s, CH2); 32.2 .t, 2JCF ˆ 22 Hz,
CH2CF2); 28.7±29.5 .m, 7CH2); 25.7 .s, CH2); 22.6
1.98 .tt, JHH ˆ 6:2 Hz, JHH ˆ 7:3 Hz, CH2). 13CNMR
d .ppm): 166.0 .s, CH2=CH±CO); 130.6 .s, CH2=CH±CO);
128.1 .s, CH2=CH±CO); 105±125 .m, 5CF2 and CF3);
2
62.8 .s, OCH2); 32.0 .t, JCF ˆ 22:1 Hz, CH2CF2); 28.7
3
.s, CH2S); 28.6 .s, CH2); 22.6 .t, JCF ˆ 4:5 Hz,
3
.t, JCF ˆ 4:1 Hz, SCH2CH2CF2). GC-MS m/z .%): 45
SCH2CH2CF2). GC-MS m/z .%): 55 .100); 69 .16); 73
.100); 87 .30); 113 .22); 119 .5); 131 .6); 159 .5); 169
.2); 393 .6); 409 .4); 420 .40).
.47); 65 .100); 69 .85); 119 .30); 131 .25); 169 .21); 478
.6); 511 .8); 525 .9).
Mixture of 1g and 2g .85/15). Yield: 91%; white solid.
Compound 5a. 1H NMR d .ppm): 6.41 .dd, JAB ˆ 1:5 Hz,
1
Compound 1g. H NMR d .ppm): 6.89±7.32 .m, 5CH);
JAX ˆ 17:3 Hz, CHA); 6.11 .dd, JAX ˆ 17:3 Hz, JBX
ˆ
3
4.08 .t, JHH ˆ 5:9 Hz, OCH2); 2.76 .m, SCH2CH2CF2
10:4 Hz, CHX); 5.83 .dd, JBX ˆ 10:4 Hz, JAB ˆ 1:5 Hz,
0
3
3
and CH2S); 2.43 .m, JHH ˆ 8:7 Hz, JHF ˆ 17:5 Hz,
CH2CH2CF2); 2.11 .m, CH2).
CHB); 5.15 .m, OCHX ); 20.80 .m, SCH2CH2CF2); 2.80
0
.m, CHA ); 2.50 .m, CHB ); 2.37 .m, CH2CF2); 1.36

Â
B. Pees et al. / Journal of Fluorine Chemistry 108 D2001) 133±142
136
0
0
.d, JM X ˆ 7 Hz, CH3M ). 13CNMR d .ppm): 166.0
.s, CH2=CH±CO); 130.6 .s, CH2=CH±CO); 128.1
.s, CH2=CH±CO); 105±125 .m, 5CF2 and CF3); 70.1 .s,
3JHF ˆ 17:6 Hz, CH2CF2); 1.32 .d, JM X ˆ 6:9 Hz, CH3M ).
0
0
0
0
13CNMR
d .ppm): 165.7 .s, CH2=CH±CO); 130.8
.s, CH2=CH±CO); 128.0 .s, CH2ˆCH±CO); 105±125
2
OCH); 37.5 .s, CH2S); 32.0 .t, JCF ˆ 22:1 Hz, CH2CF2);
.m, 7CF2 and CF3); 68.3 .s, OCH2); 38.9 .s, CHS); 32.4
3
2
3
22.6 .t, JCF ˆ 4:5 Hz, SCH2CH2CF2); 18.9 .s, CH3). GC-
.t, JCF ˆ 21:9 Hz, CH2CF2); 21.5 .t, JCF ˆ 4:2 Hz,
SCH2CH2CF2); 17.8 .s, CH3). GC-MS m/z .%): 41 .30);
45 .15); 55 .100); 69 .12); 74 .80); 101 .8); 113 .5); 119 .4);
131 .4); 169 .2); 219 .1); 501 .6); 520 .10).
MS m/z .%): 55 .100); 69 .8); 73 .31); 87 .8); 113 .4); 159
.2); 169 .3); 393 .8); 420 .43).
1
Compound 3b. Yield: 83%; orange liquid; H NMR d
.ppm): 6.39 .dd, JAB ˆ 1:5 Hz, JAX ˆ 17:3 Hz, CHA); 6.11
Mixture of 3e and 4e .95/05). Yield: 54%; yellow liquid.
Compound 3e. 1H NMR d .ppm): 6.40 .dd, JAB ˆ 1:2 Hz,
.dd, JAX ˆ 17:3 Hz, JBX ˆ 10:3 Hz, CHX); 5.80 .dd, JBX
ˆ
10:3 Hz, JAB ˆ 1:5 Hz, CHB); 4.14 .t, JHH ˆ 6:7 Hz,
JAX ˆ 17:2 Hz, CHA); 6.11 .dd, JAX ˆ 17:2 Hz, JBX
ˆ
3
OCH2); 2.73 .tt, .4JHF), JHH ˆ 9:0 Hz, SCH2CH2CF2);
10:4 Hz, CHX); 5.82 .dd, JBX ˆ 10:4 Hz, JAB ˆ 1:2 Hz,
3
2.55 .t, JHH ˆ 7:3 Hz, CH2S); 2.37 .tt, JHH ˆ 9:0 Hz,
3JHF ˆ 18:1 Hz, CH2CH2CF2); 1.56 .m, 3CH2); 1.28
.m, 6CH2). 13CNMR d .ppm): 166.2 .s, CH2=CH±CO);
130.1 .s, CH2=CH±CO); 128.6 .s, CH2=CH±CO); 105±125
.m, 5CF2 and CF3); 64.6 .s, OCH2); 32.5 .s, CH2S); 32.2
CHB); 4.18 .t, J ˆ 6:1 Hz, OCH2); 2.73 .tt, .4JHF), JHH
ˆ
3
3
8:9 Hz, SCH2CH2CF2); 2.60 .t, J ˆ 6:8 Hz, CH2S); 2.37 .tt,
3JHH ˆ 8:9 Hz, JHF ˆ 17:2 Hz, CH2CH2CF2); 1.76 .m,
3
2CH2). 13CNMR d .ppm): 166.0 .s, CH2=CH±CO);
130.2 .s, CH2=CH±CO); 128.4 .s, CH2=CH±CO); 105±
125 .m, 7CF2 and CF3); 63.7 .s, OCH2); 32.0 .t,
2JCF ˆ 22:1 Hz, CH2CF2); 31.6 .s, CH2S); 27.6 .s, CH2);
2
.t, JCF ˆ 22:0 Hz, CH2CF2); 28.4±29.5 .m, 8CH2); 25.8
3
.s, CH2); 22.5 .t, JCF ˆ 4:0 Hz, SCH2CH2CF2).
3
Mixture of 3d and 5d .90/10 ‡ traces of 4d). Yield: 83%;
orange liquid.
25.7 .s, CH2); 22.4 .t, JCF ˆ 3:8 Hz, SCH2CH2CF2).
Compound 4e. 1H NMR d .ppm): 6.40 .dd, JAB ˆ 1:2 Hz,
Compound 3d. 1H NMR d .ppm): 6.40 .dd, JAB ˆ 1:2 Hz,
JAX ˆ 17:2 Hz, CHA); 6.11 .dd, JAX ˆ 17:2 Hz, JBX
ˆ
JAX ˆ 17:3 Hz, CHA); 6.11 .dd, JAX ˆ 17:3 Hz, JBX
ˆ
10:4 Hz, CHX); 5.82 .dd, JBX ˆ 10:4 Hz, JAB ˆ 1:2 Hz,
CHB); 4.18 .m, OCH2); 2.90 .m, CHS); 2.73 .m,
SCH2CH2CF2); 2.37 .m, CH2CF2); 1.76 .m, CH2); 1.37
.d, J ˆ 4:4 Hz, CH3).
10:4 Hz, CHX); 5.83 .dd, JBX ˆ 10:4 Hz, JAB ˆ 1:2 Hz,
CHB); 4.26 .t, J ˆ 6:1 Hz, OCH2); 2.73 .tt, .4JHF),
3
JHH ˆ 8:7 Hz, SCH2CH2CF2); 2.65 .t, JHH ˆ 7:2 Hz,
CH2S); 2.40 .tt, JHH ˆ 8:7 Hz, 3JHF ˆ 17:4 Hz,
CH2CH2CF2); 1.98 .tt, J ˆ 6:1 Hz, J ˆ 7:2 Hz, CH2). 13C
NMR d .ppm): 165.9 .s, CH2=CH±CO); 130.4 .s, CH2=CH±
CO); 128.2 .s, CH2=CH±CO); 105±125 .m, 7CF2 and CF3);
Compound 3f. Yield: 82%; white solid; mp 378C; H
1
NMR d .ppm): 6.40 .dd, JAB ˆ 1:6 Hz, JAX ˆ 17:4 Hz,
CHA); 6.12 .dd, JAX ˆ 17:4 Hz, JBX ˆ 10:3 Hz, CHX);
5.81 .dd, JBX ˆ 10:3 Hz, JAB ˆ 1:6 Hz, CHB); 4.15
2
3
62.7 .s, OCH2); 32.0 .t, JCF ˆ 22:1 Hz, CH2CF2); 28.6
.t, JHH ˆ 6:7 Hz, OCH2); 2.73 .tt, .4JHF), JHH ˆ 8:6 Hz,
3
3
.s, CH2S); 28.5 .s, CH2); 22.5 .t, JCF ˆ 4:2 Hz,
SCH2CH2CF2); 2.55 .t, JHH ˆ 7:3 Hz, CH2S); 2.37
3
SCH2CH2CF2). GC-MS m/z .%): 41 .34); 45 .22); 47
.13); 55 .100); 69 .20); 73 .80); 89 .20); 113 .14); 119
.6); 131 .5); 169 .2); 219 .1); 478 .2); 493 .3); 507 .2); 520
.25); 537 .1).
.tt, JHH ˆ 8:6 Hz, JHF ˆ 17:3 Hz, CH2CH2CF2); 1.60
.m, 3CH2); 1.28 .m, 6CH2). 13CNMR d .ppm): 166.3
.s, CH2=CH±CO); 130.3 .s, CH2=CH±CO); 128.7
.s, CH2=CH±CO); 105±125 .m, 7CF2 and CF3); 64.7
Compound 5d. 1H NMR d .ppm): 6.40 .dd, JAB ˆ 1:5 Hz,
.s, OCH2); 32.3 .s, CH2S); 32.2 .t, JCF ˆ 22:0 Hz,
2
JAX ˆ 17:4 Hz, CHA); 6.10 .dd, JAX ˆ 17:4 Hz, JBX
ˆ
CH2CF2); 28.2±29.4 .m, 8CH2); 25.8 .s, CH2); 22.6 .t,
3JCF ˆ 4:4 Hz, SCH2CH2CF2). GC-MS m/z .%): 55
.100); 69 .31); 81 .16); 119 .2); 131 .2); 152 .5); 169
.2); 185 .59); 225 .2); 239 .3); 257 .26); 409 .1); 455 .1);
493 .5); 507 .1); 535 .1).
10:4 Hz, CHX); 5.83 .dd, JBX ˆ 10:4 Hz, JAB ˆ 1:5 Hz,
X0
B
CH ); 5.1 .m, OCH ); 2.80 .tt, .4JHF), JHH ˆ 8:7 Hz,
0
0
SCH2CH2CF2); 2.74 .m, CHA ); 2.47 .m, CHB ); 2.38 .tt,
3
0
0
JHH ˆ 8:7 Hz,0 JHF ˆ 17:3 Hz, CH2CF2); 1.36 .d, JM X
ˆ
6:3 Hz, CH3M ). 13CNMR d .ppm): 165.5 .s, CH2=CH±
CO); 130.7 .s, CH2=CH±CO); 128.5 .s, CH2=CH±CO);
105±125 .m, 7CF2 and CF3); 70.1 .s, OCH); 37.5 .s,
Method 2 .for a, b, d, f). In a three necked ¯ask ®tted with
a stirrer and a thermometer were placed under nitrogen 1.25
equiv. of acryloyl chloride, 250 ppm of HQME and anhy-
drous dichloromethane .freshly distilled over CaCl2,
10 ml gÀ1 of acryloyl chloride) or toluene. The ¯ask was
surrounded by a ice bath cold enough to lower the tempera-
ture of the mixture close to 08C. A solution of 1 equiv. of 2-
per¯uoroalkyl-ethyl o-hydroxy-alkyl sul®de and 1.5 equiv.
of triethylamine .freshly distilled over CaH2) in anhydrous
dichloromethane .freshly distilled over CaCl2) or toluene
was added cautiously, under stirring. After re¯uxing for
12 h, the resulting mixture was ®ltered and the organic phase
treated with NaHCO3 10%, NaOH 10% and washed one
time with water to obtain pH > 10. Then the solution was
2
CH2S); 32.1 .t, JCF ˆ 22:1 Hz, CH2CF2); 23.4 .t,
3JCF ˆ 4:3 Hz, SCH2CH2CF2); 18.9 .s, CH3). GC-MS m/z
.%): 41 .12); 45 .12); 55 .100); 69 .12); 73 .40); 113 .4); 119
.4); 131 .3); 169 .2); 219 .1); 478 .2); 493 .2); 520 .20).
Compound 4d. 1H NMR d .ppm): 6.43 .dd, JAB ˆ 1:5 Hz,
JAX ˆ 17:6 Hz, CHA); 6.13 .dd, JAX ˆ 17:6 Hz, JBX
ˆ
10:4 Hz, CHX); 5.87 .dd, JBX ˆ 10:4 Hz, JAB ˆ 1:5 Hz,
0
CHB); 4.29 .dd, JA B ˆ 11:1 Hz, JA X ˆ 6:1 Hz,0 CHA );
0
0
0
0
4.14 .dd, JA B ˆ 11:1 Hz, JB X ˆ 7:0 Hz, CHB ); 3.08
0
0
0
0
0
0
0
0
0
0
.ddt,0 JA X ˆ 6:1 Hz, JB X ˆ 7:0 Hz, JM X ˆ 6:9 Hz,
CHX S); 2.85 .m, SCH2CH2CF2); 2.38 .tt, JHH ˆ 8:8 Hz,

Â
B. Pees et al. / Journal of Fluorine Chemistry 108 D2001) 133±142
137
dried over anhydrous Na2SO4 and solvent and triethylamine
were evaporated under vacuum.
Mixture of 3a and 4a .90/10). Yield: 80%, yellow liquid;
bp 408C/10À1 mbar.
Compound 3a. NMR and GC-MS characterizations as
.m, 7CF2 and CF3); 66.0 .s, OCH); 41.6 .s, CH2S); 32.2
2
3
.t, JCF ˆ 22:1 Hz, CH2CF2); 23.0 .t, JCF ˆ 4:4 Hz,
SCH2CH2CF2); 22.0 .s, CH3). GC-MS m/z .%): 45 .100);
47 .46); 59 .28); 61 .52); 69 .20); 119 .8); 131 .7); 169 .3);
475 .1); 494 .12); 523 .2).
above.
Method 5 .for 2d). The acid 7d was prepared by reacting
1-iodo-2-per¯uorooctyl-ethane to thiolactic acid, according
to method 4 .except for the use of 2.4 equiv. of NaOH and the
®nal reaction mixture was poured into a large amount of HCl
1N). A mixture of 1.25 equiv. of LiAlH4 and anhydrous
tetrahydrofuran .freshly distilled over Na) was purged with
nitrogen. At room temperature, a solution of 1 equiv. of 7d in
tetrahydrofuran .freshly distilled over Na) was cautiously
added for 1 h. Then, the reaction was carried out under re¯ux
for additional 12 h. The resulting mixture was cooled to 08C
and a saturated solution of NH4Cl was slowly added drop-
wise with vigorous stirring. This mixture was ®ltered and the
precipitate was abundantly washed with chloroform. The
organic layer was separated and dried over anhydrous
Na2SO4. Solvents were distilled off under vacuum.
Compound 7d. Yield: 75%; brown solid; 1H NMR d
.ppm): 3.45 .q, J ˆ 7:1 Hz, CH); 2.91 .m, SCH2CH2CF2);
2.43 .tt, 3JHH ˆ 8:7 Hz, 3JHF ˆ 17:5 Hz, CH2CF2); 1.48 .d,
3JHH ˆ 7:1 Hz, CH3). 13CNMR d .ppm): 179.5 .s, COOH);
105±125 .m, 7CF2 and CF3); 41.1 .s, CHS); 31.8 .t,
2JCF ˆ 22:2 Hz, CH2CF2); 22.4 .t, 3JCF ˆ 4:2 Hz,
SCH2CH2CF2); 16.3 .s, CH3).
Compound 4a. 1H NMR d .ppm): 6.41 .dd, JAB ˆ 1:5 Hz,
JAX ˆ 17:6 Hz, CHA); 6.11 .dd, JAX ˆ 17:6 Hz, JBX
ˆ
10:4 Hz, CHX); 5.83 .dd, JBX ˆ 10:4 Hz, JAB ˆ 1:5 Hz,
0
0
0
CHB); 4.20 .m, CHA ); 4.10 .m, CHB ); 3.02 .m, CHX S);
2.70 .m, SCH2CH2CF2); 2.40 .m, CH2CF2); 1.20 .d,
0
JM X ˆ 6:5 Hz, CH3M ).
0
0
Compound 3b. Yield: 85%; orange liquid; NMR char-
acterization as above.
2.2.4. Preparation of 2-perfluoroalkyl-ethyl-o-
hydroxy-alkyl sulfide
Method 3 .for 1a, 1c, 1d). To a mixture of 1 equiv. of 2-
per¯uoroalkyl-ethanethiol and 1.1 equiv. of K2CO3 in etha-
nol/water .90/10, v/v), was added a solution of 1.1 equiv. of
o-hydroxy-alkyl halide in absolute ethanol at 758Cunder
nitrogen. Re¯uxing was continued for 6 h. After cooling to
room temperature, the reaction mixture was poured into a
large amount of dilute Na2CO3 aqueous solution and the
precipitate was dissolved in chloroform. The chloroform
layer was washed neutral with water, dried over anhydrous
Na2SO4 and the solvent was evaporated under vacuum.
Compound 1a. Yield: 98%; yellow liquid; NMR and GC-
MS characterizations as above.
Compound 2d. Yield: 82%; brown solid; NMR and GC-
MS characterizations as above.
1
Compound 1c. Yield: 82%; yellow solid; mp 738C; H
3
È
2.2.5. Preparation of prop-2-en-1-oõc acid 2-
perfluoroalkyl-ethyl thioalkyl ester
NMR d .ppm): 3.79 .t, JHH ˆ 5:8 Hz, OCH2); 2.79 .m,
CH2S
&
SCH2CH2CF2); 2.39 .tt, 3JHH ˆ 8:8 Hz,
3JHF ˆ 17:6 Hz, CH2CH2CF2); 1.99 .broad s, shifted with
Compounds 3a and 3d were prepared according to
method 1 .Fischer esteri®cation) while compounds 4d
and 5d according to method 2 .acryloyl chloride route).
Compound 3a. Yield: 80%; yellow liquid; NMR and
GC-MS characterizations as above.
Compound 3d. Yield: 78%; yellow liquid; NMR and
GC-MS characterizations as above.
Compound 4d. Yield: 78%; brown liquid; NMR and
GC-MS characterizations as above.
dilution, OH). 13CNMR d .ppm): 105±125 .m, 7CF2 and
2
CF3); 60.7 .s, OCH2); 35.4 .s, CH2S); 32.2 .t, JCF
ˆ
3
22:0 Hz, CH2CF2); 22.6 .t, JCF ˆ 4:5 Hz, SCH2CH2CF2).
GC-MS m/z .%): 45 .100); 69 .30); 77 .20); 91 .9); 119 .7);
131 .6); 169 .2); 441 .1); 493 .8); 524 .3).
Compound 1d. Yield: 91%; yellow solid; NMR and
GC-MS characterizations as above.
Method 4 .for 6d). A mixture of 1 equiv. of 1-iodo-2-
per¯uorooctyl-ethane, 1.2 equiv. of NaOH, 1.1 equiv. of 1-
mercapto-propan-2-ol and ethanol/water .90/10, v/v) was
re¯uxed under nitrogen for 6 h. The cooled mixture was
diluted with a large amount of diluted Na2CO3 aqueous
solution and the non-aqueous phase was taken up in chloro-
form, washed to pH 7±8 and dried over anhydrous Na2SO4.
The solvent was evaporated under vacuum yielding a yellow
solid.
Compound 5d. Yield: 83%; orange liquid; NMR and
GC-MS characterizations as above.
3. Results and discussion
The synthesis of 2-.per¯uoroalkyl)-ethyl alkyl thioethers
is usually performed in a two step-procedure. The ®rst one
concerns the preparation of 2-.per¯uoroalkyl)-ethyl o-
hydroxy-alkyl thioether A followed by its esteri®cation
leading to the corresponding acrylic monomer.
Compound 6d. Yield: 83%; yellow solid; 1H NMR d
.ppm): 3.90 .ddt, JBX ˆ 8:4 Hz, JAX ˆ 3:8 Hz, JMX
ˆ
6:1 Hz, OCHX); 2.78 .tt, .4JHF), JHH ˆ 8:8 Hz,
SCH2CH2CF2); 2.74 .dd, JAB ˆ 13:6 Hz, JAX ˆ 3:8 Hz,
CHA); 2.52 .dd, JAB ˆ 13:6 Hz, JBX ˆ 8:4 Hz, CHB);
3
3
2.40 .tt, JHH ˆ 8:8 Hz, JHF ˆ 17:5 Hz, CH2CF2); 1.26
.d, JMX ˆ 6:1 Hz, CH3M). 13CNMR d .ppm): 105±125

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B. Pees et al. / Journal of Fluorine Chemistry 108 D2001) 133±142
138
Obtaining the alcohol by nucleophilic substitution of the
halogen atom X by the alkali salt of an o-hydroxy-alkylthio-
late is a well-known reaction [51,52].
However, this process does not enable one to easily
achieve a wide range of monomers. The size of the n
methylene spacer between the hydroxy group and the
thioether bridge of the resulting monomer depends on the
structure of the involved o-mercapto alcohol; but the diver-
sity of these commercially available reactants is poor and
their synthesis is not easy [53].
Scheme 2.
A previous article reports the radical addition of an o-
mercaptoalcohol to the double bond of an allylic monomer
bearing a per¯uorinated end-group [48] but this synthesis
has the same limitation as that above.
products have been well-identi®ed as the eventual by-pro-
ducts and are described below .Scheme 2).
Our present study relies on the radical addition of two
different 2-per¯uoroalkyl-ethanethiols .m ˆ 6 or 8) onto
various o-unsaturated alcohols containing 3, 4 or 11 carbon
atoms, as follows:
3.1. Radical addition of 2-perfluoroalkyl-ethane-
thiol to an o-unsaturated alcohol
Usually, in the course of the radical initiation .that occurs
either thermally or photochemically) the thiyl radical gen-
erated from the homolytic cleavage of the S±H bond of 2-
per¯uoroalkyl-ethanethiol can add onto the double bond of
the o-unsaturated alcohol [54]. For the present reaction,
AIBN was chosen as the thermal initiator, at 808C , in
solution in cyclohexane or acetonitrile [55,56]. Such initia-
tion enabled us to obtain a wide variety of 2-per¯uoroalkyl-
ethyl-o-hydroxy-alkyl thioethers in good yields .65±90%,
after puri®cation) .Scheme 3). However, in certain cases, the
presence of isomers was noted as a consequence of both
possible attack sites of the thiyl radical toward the double
bond of the o-unsaturated alcohol .Scheme 4).
Thus, a wide range of original o-hydroxy monomers
bearing a thioether bridge and a per¯uorinated end-group
have been synthesized, as precursors of novel ¯uorinated
acrylates .Scheme 1). These various intermediates and
1
The presence of branched isomer 2 was detected by H
NMR spectroscopy: the doublet centered at 1.3 ppm is
characteristic of the methyl group and can be neatly dis-
tinguished in the case of reactions involving allyl alcohol
and but-3-en-1-ol. The assignment of that signal to the
branched isomer was con®rmed by the NMR characteriza-
tion of pure 2d isomer synthesized from another process
.Scheme 3). Indeed, alcohols 1a, 1d and 2d were prepared
by ionic reactions which form desired isomers selectively. In
the case of alcohol 2d, 2-mercapto-propan-1-ol is not a
commercially available reactant; hence, nucleophilic sub-
stitution of the iodine atom of 1-iodo-2-per¯uorooctyl-
ethane by sodium mercaptolactate was achieved. Acid 7d
thus prepared was then reduced into alcohol 2d in the
presence of lithium aluminum hydride.
Interestingly, we noted that the longer the o-unsaturated
alcohols, the lower the amount of isomer 2. This isomer was
not produced when 10-undecen-1-ol was used, whatever the
2-per¯uoroalkyl-ethanethiol .m ˆ 6 or 8). Such an observa-
tion can be interpreted by the study of the relative stability of
the different intermediate radicals. As shown in Scheme 4,
the double bond exhibits two possible attack sites .a and b)
for the thiyl radical, leading to both intermediate radicals.
Intrinsically, secondary radical 1ꢀ is more stable than
‡
primary 2ꢀ, as a secondary carbocation .R2CH ) is more
Scheme 1.

Â
B. Pees et al. / Journal of Fluorine Chemistry 108 D2001) 133±142
139
Scheme 3.
‡
stable than a primary one .RCH2 ) [57,58]. This explains
group, the more destabilized the radical. Taft [59] showed
that the inductive effect of an electron-withdrawing group
decreases 2.7 times for each intercalated methylenic unit;
thus in the case of an alcohol containing a small number of
carbon atoms .n ˆ 3 or 4), the destabilization of 1ꢀ radical
by the close presence of the hydroxyl function is greater than
in the case of 2ꢀ radical containing a further methylenic
group. This destabilization of 1ꢀ radical allows 2ꢀ radical to
be formed and to lead to a non-negligible amount of
branched isomer 2ꢀ. As for longer and longer o-unsaturated
alcohols, the methylene number is thus increased and the
difference between 1ꢀ and 2ꢀ radicals decreases. This
explains why the amount of 2ꢀ isomer decreases when
the length of the unsaturated alcohol increases.
the major amount of isomer 1 .anti Markovnikov product) in
the resulting mixture of radical addition of a mercaptan onto
an o-unsaturated alcohol.
However, the hydroxyl group may have a certain in¯uence
on the stability of these radicals. The more the radical
undergoes the electron-withdrawing effect of an adjacent
We have veri®ed this hypothesis by carrying out the
radical addition of 2-per¯uorooctyl-ethanethiol to the dou-
ble bond of allyl phenyl ether under the same conditions as
those above .Scheme 2); only 1H NMR spectra data appear
in this present article. The intermediate radical of 1ꢀ type is
thus in the b-position to a phenoxy function whose electron-
withdrawing effect is higher than that of a hydroxyl func-
tion; the destabilization is stronger and isomer 2 is obtained
in higher amount .15%). Besides, Brace [60] has previously
investigated the radical addition of 2-per¯uoroalkyl-etha-
nethiols to alkene and has reported that the reaction between
2-per¯uorohexyl-ethanethiol and hexene led to 2-per¯uor-
ohexyl-ethyl hexyl sul®de with a small amount of 2-per-
¯uorohexyl-ethyl-1-methyl-pentyl sul®de .2.29%). This
shows that the use of an ole®n without an electron-with-
drawing group close to the double bond leads mainly to the 1
type isomer.
Nevertheless, by carrying out the radical addition of 2-
per¯uorooctyl-ethanethiol onto the double bond of vinyl
acetate .Scheme 2), we have shown that the amount of
isomer 2 was negligible although the electron-withdrawing
effect group was directly linked to the double bond, as
previously described by Brace [60]. This can be explained
Scheme 4.

Â
B. Pees et al. / Journal of Fluorine Chemistry 108 D2001) 133±142
140
isomer mixture), the nature of the compounds obtained was
different.
Although esteri®cation reactions of 1b and 1f alcohols
and 1e/2e mixture led to desired acrylic monomers, pure 3b
and 3f acrylates and 3e/4e isomer mixture, respectively, in
expected amounts .95 and 5% of linear and branched
compounds, respectively), esteri®cation of 1a/2a and 1d/
2d isomer mixtures led to more surprising and unexpected
linear .3) and branched .5) isomers .Scheme 1).
In the case of 1d/2d mixture, a careful study of the 13C
NMR spectrum of the acrylic monomer mixture compared to
those of pure compounds 3d, 4d and 5d enabled us to
characterize without ambiguity the nature of the obtained
mixture; the relative amounts of isomers were assessed by
1H NMR spectroscopy.
Scheme 5.
by the stabilization of the intermediate radical of 1ꢀ as
depicted in Scheme 5.
Further, whatever the o-unsaturated alcohol used, a thio-
2-.per¯uoroalkyl)-ethyl group in a b-position in the radical
in¯uences 1ꢀ and 2ꢀ intermediates in the same way. The size
of the per¯uorinated chain does not in¯uence the proportion
of both isomers.
To understand the formation of isomer 5 instead of that of
expected isomer 4 .obtained in traces), we found it worth
while to carry out the esteri®cation reaction under the same
conditions as those used for alcohol 1c containing two
methylene groups located between the hydroxyl function
and the sulfur atom. Indeed, that reaction led to a mixture
still containing a non-negligible amount of the starting
alcohol and various by-products. Rondestvedt and Thayer
[51] also noted such unexpected low yields .19%) in a
similar study and reported that an uncontrolled polymeriza-
tion occurred. In the same way, Cerf et al. [61] also observed
a decrease in the yield of the esteri®cation reaction, in an
acidic medium, of several non-¯uorinated-b-hydroxyl
sul®des. Furthermore, Schies et al. [62] investigated the
behavior, in acidic medium, of certain functionalized sulfur-
containing compounds possessing two methylenic groups
between the sulfur atom and a nucleophobic group. The
formation of a thiiranium ion was assumed. This can be
explained by the high nucleophilicity and polarizability of
the sulfur atom and, in the case of alcohols, by the ability of
protonation of the hydroxyl function, leading to an elimina-
tion of intramolecular water .Scheme 6) [62].
3.2. Esterification of 2-Dperfluoroalkyl)-ethyl
o-hydroxy-alkyl sulfide
The second step of the synthesis of acrylic monomers
relies on the esteri®cation of alcohols .pure or as an isomer
mixture). This was performed by two methods .Scheme 1):
either the Fisher esteri®cation of acrylic acid .method 1) or
acylation in the presence of acryloyl chloride .method 2).
The esteri®cation reaction according to the latter method
allowed us to obtain desired monomer 3b .n ˆ 11) selec-
tively or a 3a/4a isomer mixture .n ˆ 3) in high yields .85
and 80%, respectively). In the case of the isomer mixture,
the amounts of both acrylic esters obtained were similar to
those of the mixture of hydroxylated isomers used .i.e. 90%
of linear compound and 10% of branched one) .Table 1).
The Fisher esteri®cation .method 1) led to surprising
results that varied according to the nature of the alcohols
.Table 2). The yields remained constant .ca. 80±85% after
puri®cation) but according to the alcohols used .pure or as an
The formation of by-products can also be explained by the
high electropositivity of the sulfur atom of the thiiranium
Table 1
Adducts from the reaction of alcohols with acryloyl chloride .method 2)
n
m
Alcohols
Esters
3
6
6
1a, 90%
1b
2a, 10%
±
3a, 90%
1b
4a, 10%
±
11
Table 2
Adducts from the reaction of alcohols with acrylic acid .method 1)
n
m
Alcohols
Esters
3
6
6
8
8
8
1a, 90%
1b
2a, 10%
±
3a, 90%
3b
±
±
5a, 10%
±
5d, 10%
11
3
1d, 90%
1e, 95%
1f
2d, 10%
2e, 5%
±
3d, 90%
3e, 95%
3f
4d, traces
4e, 5%
4
±
±
11
±

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B. Pees et al. / Journal of Fluorine Chemistry 108 D2001) 133±142
141
Scheme 6.
Scheme 7.
ion, generating two possible attack sites by nucleophilic
species present in the medium .i.e. sul®de, acid, alcohol)
[63] on both carbon atoms adjacent to the thiirane ring.
The synthesis of the corresponding acrylic monomer can
thus be performed in neutral .or alkaline) medium, only, to
avoid the formation of the thiiranium ion. Hence, esteri®ca-
tion reaction of alcohol 1c was achieved by acryloyl chloride
in the presence of triethylamine leading to pure monomer 3c
in 80% yield. This clearly shows the in¯uence of thiiranium
ion on the esteri®cation of a b-hydroxylated sul®de. Further-
more, esteri®cation by acrylic acid of alcohol 1d gave
compound 3d speci®cally, in 78% yield after puri®cation.
In the case of the isomers mixture, alcohol 2d led mainly to
acrylate 5d. Similarly, for the esteri®cation of the 1e/2e
isomer mixture, branched isomer 2e yielded expected ester
4e: this clearly shows that the branched structure of alcohol
2d does not in¯uence the rearrangement allowing formation
of the product 5d. Next, acylation reaction in the presence of
acryloyl chloride of alcohol 2d enabled us to obtain expected
branched monomer 4d selectively, in 78% yield. This reac-
tion was carried out in an alkali medium and shows that
isomer 5d is formed when the reaction occurs in acid
medium.
salts, respectively. Comparing these studies, we suggest the
following structure of the intermediate that may explain the
major formation of 5d above about that of 4d in the Fisher
esteri®cation of alcohols 2d and 5d .Scheme 7). A
CmF2m‡1C2H4-group linked to the sulfur atom has a slightly
electron-withdrawing behavior. This latter with a weaker
electronic effect, can attract the electrons of both carbon
atoms of the ring. The more branched carbon atom is
stabilized by the donor inductive effect of the methyl
group. The charge of this carbon atom is thus more stabilized
and consequently this atom is the major site of attack. That
hypothesis has been con®rmed by esterifying alcohol 6d by
acrylic acid .method 1) that led to the same mixture .4d/5d,
80/20) as that obtained when the esteri®cation was carried
out with alcohol 2d .Scheme 8).
The study, dealing with compounds containing a per¯uor-
ooctyl end-group can also be performed for those bearing a
per¯uorohexyl group. We have also noted the formation of
ester 5a in the course of the esteri®cation of the 1a/2a isomer
mixture.
4. Conclusion
It can also be expected that in the course of the esteri®ca-
tion of 1d/2d mixture from method 1, branched isomer 2d,
because of both its b-hydroxyl-containing sul®de structure
and the experimental conditions in acidic media, led to a
thiiranium ion that produced ester 5d by reacting with
acrylic acid. The traces of product 4d of direct esteri®cation
can be explained by the presence of both sites of nucleo-
philic attack .Scheme 7) on the thiiranium ion. The main
attack of acrylic acid onto the more substituted carbon atom
of the sulfur-containing ring con®rms both Mueller's [64]
and, Baig and Owen's [65] results for the ring opening of the
asymmetric thiiranium ring by a chloride ion or by acetate
This work reports ways of preparation of various 2-
.per¯uoroalkyl)-ethyl alkyl thioether acrylic monomers
from alcohols containing a reactive double bond. The wide
range of commercially available unsaturated alcohols
enabled us to obtain numerous monomers. However, several
issues inherent to the different ways of synthesis, may lead
to an isomer mixture of variable composition, according to
the nature of the alcohol. It has also been possible to
investigate the in¯uence of the formation of the thiiranium
ion when the esteri®cation of b-sulfur-containing alcohol
occurred in acidic medium.
Scheme 8.

Â
B. Pees et al. / Journal of Fluorine Chemistry 108 D2001) 133±142
142
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