Reactions of 2-(perfluoroalkyl)ethane thiols with 1,6-heptadiene and 4-substituted 1,6-heptadienes: The synthesis of RFethanethio- cyclopentanoic and -dioic acids; and, "geminal-twin-tail" bis-(perfluoroalkylethanethio)alkanoic acids

Article abstract of DOI:10.1016/j.jfluchem.2004.03.012

Kinetic analysis of the free radical addition of n-C₆F ₁₃I to 1,6-heptadiene gives a rate ratio of cyclization to addition (k_d1/k_c) of 0.568 at 70°C; thus, the rate of cyclization (k_c) is twice that of iodine transfer (k_d1). By contrast, for n-C₆F₁₃CH₂CH₂SH (k_d1/k_c) = 14.4 at 70°C, and radical transfer of H from the thiol is 14.4 times the faster than cyclization. Substitution at the center of 1,6-heptadiene has a profound effect on the linear/cyclic adduct ratio. For the addition of n-C₃F₇I (R_FI:diene= 2:0) the adduct ratios dramatically decrease in the order: 1,6-heptadiene (1.17) > 4-carboxy-1,6-heptadiene (0.0613) > 4,4-bis-ethoxycarbonyl-1,6- heptadiene (<0.001). Bis-addition to the 4,4-substituted dienes is strongly disfavored, and the desired "geminal-twin-tail" [R_F(CH ₂)₃]₂CHCO₂R, or [R _F(CH₂)₃]₂C(CO₂R) ₂ must be synthesized by other means. For the reaction of R _FCH₂CH₂SH with the dienes (1:1), the respective adduct ratios are 11.3 (n-C₆F₁₃), 0.370 (n-C ₈F₁₇), and 0.0716 (n-C₆F₁₃). However, adding the 4-carboxy-1,6-heptadiene slowly to four mols of n-C ₈F₁₇CH₂CH₂SH yields 98% of the geminal bis-adduct [R_FCH₂CH₂S(CH ₂)₃]₂CHCO₂H, which is a new, fluorophilic, geminal-twin-tail acid.

Full text of DOI:10.1016/j.jfluchem.2004.03.012

Journal of Fluorine Chemistry 126 (2005) 7–15
Reactions of 2-(perfluoroalkyl)ethane thiols with 1,6-heptadiene and
4-substituted 1,6-heptadienes: the synthesis of RFethanethio-
cyclopentanoic and -dioic acids; and, ‘‘geminal-twin-tail’’
bis-(perfluoroalkylethanethio)alkanoic acids$
Neal O. Brace*
Wheaton College, Wheaton, IL 60187 USA
Received 31 October 2003; received in revised form 1 March 2004; accepted 12 March 2004
Available online 30 November 2004
Abstract
Kinetic analysis of the free radical addition of n-C6F13I to 1,6-heptadiene gives a rate ratio of cyclization to addition (kd1/kc) of 0.568 at
70 8C; thus, the rate of cyclization (kc) is twice that of iodine transfer (kd1). By contrast, for n-C6F13CH2CH2SH (kd1/kc) ¼ 14.4 at 70 8C, and
radical transfer of H from the thiol is 14.4 times the faster than cyclization. Substitution at the center of 1,6-heptadiene has a profound effect on
the linear/cyclic adduct ratio. For the addition of n-C3F7I (RFI:diene ¼ 2 : 0) the adduct ratios dramatically decrease in the order: 1,6-
heptadiene (1.17) > 4-carboxy-1,6-heptadiene (0.0613) > 4,4-bis-ethoxycarbonyl-1,6-heptadiene (<0.001). Bis-addition to the 4,4-substituted
dienes is strongly disfavored, and the desired ‘‘geminal-twin-tail’’ [RF(CH2)3]2CHCO2R, or [RF(CH2)3]2C(CO2R)2 must be synthesized by
other means. For the reaction of RFCH2CH2SH with the dienes (1:1), the respective adduct ratios are 11.3 (n-C6F13), 0.370 (n-C8F17), and
0.0716 (n-C6F13). However, adding the 4-carboxy-1,6-heptadiene slowly to four mols of n-C8F17CH2CH2SH yields 98% of the geminal bis-
adduct [RFCH2CH2S(CH2)3]2CHCO2H, which is a new, fluorophilic, geminal-twin-tail acid.
# 2004 Elsevier B.V. All rights reserved.
Keywords: Thiol addition reactions; 1,6-Heptadiene cyclization; Linear/cyclic adduct; Fluorophilic; Geminal-twin-tail 2,2-[bis-(perfluoroalkyl)alk-
ylthio]ethanoic acid
1. Introduction
ducts are not observed [3]. However, with 1,6-heptadiene
(2), or a 4-substituted 1,6-heptadiene, cyclization to a five-
membered ring occurs readily [5–7]. This tendency is driven
in part by the kinetics of the reaction (see Scheme 1), and in
part by the non-bonded interactions of 4-substituents with
adjacent carbon atoms in an extended chain conformation
[3,4]. It is ascertained from Table 1 that the linear/cyclic
adduct ratio from 2 is directly proportional to the conc of 1:
[3 þ 5]/[4a,b] ¼ (kd1)/(kc)[1] þ intercept [3,6–8]. And, by
least squares, the (kd1/kc) ¼ 0.568 at 70 8C [8].1 Thus, the
rate of transfer (kd1) of mono adduct radical 3 is only about
half that of cyclization (kc). Further experimentation shows
that the linear/cyclic adduct ratio falls precipitously from
1.17 with 2, to 0.0613 with CH2¼CHCH2CY1Y2CH2CH¼
CH2 (Y ¼ H, Y ¼ CO2Et), Table 2 [10]. With the bis-4,4-
substituted 1,6-heptadienoic ester, entries 3, and 4, neither
the linear mono nor the bis-adduct is a significant product
[9,10]. Thus, a different sequence of steps is devised for
1.1. Radical addition reactions of perfluoroalkyl iodides
(RFI), and the synthesis of twin-tail, long RF chain
compounds
Radical addition and cyclization reactions are a field of
great interest and importance [1]. The synthesis of twin-tail,
long RF chain compounds by the free radical reaction of RFI
(1) is recently reviewed [2–4]. When adding 1 to an a,o-
alkadiene, in which the intervening segments are smaller
than three or larger than four carbon atoms, cyclized pro-
$ This paper is presented, in part, at the Gordon Research Conference
on ‘‘Free Radical Reactions’’, 2–26 July 1991, Colby-Sawyer College,
New London, NH; and, in part as ‘‘2-(perfluoroalkyl)ethane thiols, a
versatile perfluoroalkylating agent,’’ at the Winter Fluorine Conference
(ACS), 25–30 January 1993, St. Petersburg Beach, Florida.
* Present address: 4433 32nd Ave N., St. Petersburg, FL 33713, USA.
Tel.: þ1-727-528-7928.
E-mail address: nobrace@gbronline.com (N.O. Brace).
1 This result is not disclosed in [8].
0022-1139/$ – see front matter # 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2004.03.012

8
N.O. Brace / Journal of Fluorine Chemistry 126 (2005) 7–15
Scheme 2. Preparation of twin-tail bis-RF-alkyl alkanoic acid 20 and
related compounds.
Scheme 1. Pathways to linear and cyclic adducts from RFl and 1,6-dienes,
rate constants for kinetic analysis.
the synthesis of
a
geminal-twin-tail acids such as
2. Results and discussion
[RF(CH2)3]2CHCOOH, Scheme 2. In part A, the single tail
RF(CH2)3CH(CO2Et)2 is prepared in very good yield by two
methods. RFI adds readily to allylmalonic ester, followed by
zinc reduction, steps (1) and (2) [9–12]. Alkylation of
malonic ester by RF(CH2)nI (n ¼ 2, 11); step (3) goes
cleanly in t-butyl alcohol, with a sterically hindered base
(t-butoxide), to afford the RF(CH2)nCH(CO2Et)2 [2,13,14].
In Part B, RF(CH2)3I (2 mol, with NaH as base in DMF
to circumvent the formation of an ether side product)
yields the geminal-twin-tail diester in one step (4)
[15,16]. Two more steps, (5) and (6), are required to reach
the [RF(CH2)3]2CHCOOH, which exhibits the anticipated
fluorophilic properties, and dissolves in super critical (sc)
CO2 or in perfluoro(methylcyclohexane [15–17]. In 1982
and 1984, RF(CH2)3I is prepared for the first time in three
steps from RFI [18,19].
2.1. The synthesis of twin-tail, long RF chain acids and
derivatives from thiol RFCH2CH2SH (6)
Already known are long RF chain acids, RF(CH2)n-
S(CH2)mCOOH and RF(CH2)nS(CH2)3CH(CO2H)CH2-
COOH, that are notable RF surfactants [20,21]. By
contrast with the multi-step syntheses of Scheme 2, a
geminal-twin-tail, long RF chain alkanoic acid, [RFCH2-
CH2S(CH2)3]2CHCOOH, is prepared in a single step from
radical addition of thiol 6 (RF ¼ n-C8F17) to 2,2-bis-(2-
propenyl)ethanoic acid, Section 2.3.1. This remarkable
and surprising result culminates an extended study of thiol
6 reactions [20–23]. This synthesis, the radical addition of
6–2, and of 6 to 4-substituted 1,6-heptadienes, are the
subjects of this paper. Of special interest are the similarities
Table 1
The reaction of [RFI] (1) and 1,6-heptadiene (2); the effect of RFI concentration on the linear to cyclic adduct ratioa
Entry
[RFI]
[3 þ 5]/[4a,b]
References
1b
2b
3b
4d
5d
6e
7e
8e
4.81c
3.50
2.29
1.47
1.32
1.00
0.50
0.25
2.78
1.70
[7]
[7]
[7]
[8]
[8]
[7]
[7]
[7]
1.30
0.92
0.70
0.370
0.189
0.131
Twin-tail perfluoroalkylethanethioetheralkanoic acids and -alkanedioic acids and their derivatives.
a Mono (3), bis (5), and cis and trans-cyclic (4a,b) adducts, with RFI ¼ n-CF3(CF2)nI (n ¼ 2 or 3) and AIBN as initiator. Regression analysis of [3 þ 5]/
[4a,b] ¼ (kd1)/(kc)[RFI] þ intercept gives (kd1)/(kc) ¼ 0.568, intercept ¼ À0.0633, and r (reliability) ¼ 0.990. This calculation is not reported in [7,8].
b Reaction of n-CF3(CF2)2I with 2, at 60 8C, Table IX [7].
c The value of [3 þ 5]/[4a,b], when calcd from the equation above, is 2.67.
d Reaction of n-CF3(CF2)3I at 70 8C, with 2, 1-hexene and AIBN [8].
e Reaction of n-CF3(CF2)2I with 2, in n-hexane at 60 8C, Table V [7].

N.O. Brace / Journal of Fluorine Chemistry 126 (2005) 7–15
9
Table 2
Radical addition of RFI (1) to 4-substituted-1,6-heptadienes, 10 and 14, in comparison with 1,6-heptadiene (2)a
Entry no.
RFI(1)
(CH2¼CHCH2)2CY1Y2
RFI/x-hpd (mol)b
Time/temp (h/8C)
Total yield (%)
Linear/cyclic
RF
[RFI]
No.
Y1
Y2
1b
2c
3d
4e
n-C3F7
n-C3F7
n-C3F7
n-C4F9
4.81
4.35
4.38
3.77
2
10c
14
14
H
H
2.00b
2.00
2.90
2.00
24/60
21/70
24/70
24/70
99.7
89.3
95.0
95.0
1.17b
H
CO2Et
CO2Et
CO2Et
0.0613
<0.00d
<0.001e
CO2Et
CO2Et
a The experimental work is recorded in [7,10–12]. Reactants are 2, ethyl 1,6-heptadiene-4-carboxylate (10; ethyl ester) and 4,4-bis-ethoxycarbonyl-1,6-
heptadiene (14).
b The linear/cyclic ratio for mol RFI/2 ¼ 2.0 is extrapolated from entries 11 to 14 in Table IX (60 8C, 24 h) [7]. The equation [linear/cyclic] ¼ m([RFI/2])
þ b gives m ¼ 0:663, b ¼ À0:157, r ¼ 0:996. Linear/cyclic is 1.17. Owing to the reversal of the displacement step, and the non-reversal of the cyclization
step, the linear/cyclic ratio decreases with long reaction time [7].
c From 10; ethyl ester, GC: [linear/cyclic] ratio ¼ 0.0613. Reduction gives iodine-free, distillable compounds in 92% yield, mol [linear/cyclic] ¼ 0.0711
[10].
d Reaction of 14 at mols 1/14 ¼ 2.90 gives no linear adduct (IR or 1H NMR). Also, with 1/14 ¼ 2.0, 93% yield of cyclic products only [10–12].
e n-C4F9I with 14 gives adducts in 95% yield [10]. Zinc and acid reduction, and, hydrolysis to diacids, give cyclic isomers with no evidence for linear
adducts [10].
and differences in the chemistry of the two fluorinated
radicals, RF, and RFCH2CH2S.
1,6-heptadienes 10 and 14, in later sections). Analogous to
that of 1, the linear/cyclic adduct ratio from 6 and 2 (with
AIBN) at 70 8C (Table 4) is defined by the equation: ([7] þ
[9])/[8a,b] ¼ (kd1/kc) [6] þ intercept [3,6–8]. And, by least
squares, ðkd1=kcÞ ¼ 14:4. Thus, the rate of transfer (kd1) of 7
with 6 (Scheme 3, step 2) is 14.4 times that of cyclization
(kc), step (3). In comparison, the bulky RFI transfers iodine
to the adduct radical 3 only half as fast as the rate of
cyclization [8]. Table 4 shows no exact correlation of percent
conversion with the linear to cyclic adduct ratio; however,
entries 2–5 suggest that [7] þ [9])/[8a,b] decreases with
increased conversion at a given [6] and mol 6/2.
2.2. Radical induced addition of thiol 6 (RF ¼ n-C6F13) to
1,6-heptadiene (2) at 70.0 8C
Addition of 6 to 1,6-heptadiene (2) provides linear and
cyclic adducts just as for the reaction of RFI. In the reactions
of 6 with diene 2 (Table 3), the linear to cyclic adduct ratio
[(7 þ 9)/8a,b] ¼ 6.33, and with mol 6/2 doubled to 1.0, this
ratio is 11.3 [23]. Scheme 3 provides a framework for
discussing the reaction of 6 with 2 (and with substituted
Table 3
Reaction of thiol 6 (C6) and 1,6-heptadiene (2) at two reactant ratios (AIBN; 70 8C)a
Entry no.
Products
GC, rt (min)
Conversion mol% at 6/2 mol
0.472b
0.964c
b
1
2
3
4
5
6
7
8h
Regio of 7d
Disulfidee
Mono-7
17.21
17.30
18.11
18.53
24.11
24.95
–
–
1.13
3.17
50.9
7.48
1.42
31.3
95.4
11.3
b
–
46.7
12.9
Cis-8; trans-8
Regio of 9f
Bis-9g
b
–
38.9
99.7
6.33
Total 7–9
Linear/cyclic
–
a Mol amounts of substances are calcd, making use of FID response factors, and based on mols of 6 charged.
b Table 1, entry 7; Table VI of [22]. Reactants are heated for 5 h at 70 8C. Side products comprise ca. 1.2%.
c Table I, entry 8 of [22]. Reactants are heated at 70 8C for 1 h.
d Probably regio isomer of 7; i.e., RFCH2CH2S(CH3)CH(CH2)3CH¼CH2 [22].
e Disulfide [C6F13CH2CH2S]2 [22].
f Probably regio isomer of 9; i.e., RFCH2CH2S(CH3)CHCH2(CH2)4SCH2CH2RF.
g The conversion to 9 is calcd from mols of 9/6, times two.
h For comparison, the linear/cyclic ratios are calcd from the linear equation of Table 4: at 6/2 ¼ 0.472, the ratio ¼ 5.64; and, at 6/2 ¼ 0.964, the ratio is
13.9.

10
N.O. Brace / Journal of Fluorine Chemistry 126 (2005) 7–15
Scheme 4. Radical addition of thiol 6 to bis-(2-propenyl)ethanoic acid 10.
2.3.1. Slow, metered addition of acid (10) to thiol 6
(RF ¼ C8); radical addition at a very high 6/10 reactant
ratio provides bis-adduct 13 in high yield and conversion
The dienoic acid 10 (25 mmol) is added very slowly
(0.624 mmol/min) to 6 (100 mmol) at 70 8C, with AIBN as
initiator, steps (1 and 2) and (5,6) of Scheme 4. With a high
concentration of 6, the transfer steps 2 and 6 of Scheme 3 will
be favored over the cyclization step (kc), and the reversal of
transfer, steps 2 and 6. The calcd mol ratio of 6/10, assuming
that none of 6 reacts, is 160 in one min, 39.3 in 5 min, and 15.1
after 10 min. If 90% of the added 10 reacts within the first min
(a likely result), the mol 6/10 ¼ 1600. In entry 1 of Table 7, at
mol 6/2 ¼ 0.93, 51.7% of 6 reacts in the first two min. In the
experiment, thiol 6 adds to either end of 10, and the bis-
addition follows to the exclusion of cyclization. The bis-
adduct [RFCH2CH2S(CH2)3]2CHCOOH (13) is isolated in
92.1% conversion and 98% yield, and is fully characterized
(see Section 2.5 for further discussion of these results).
Amphiphilic, geminal-twin-tail, long RF chain compounds
such as 13 confer fluorophilic properties to solid surfaces, to
the surface at the interface of two liquids, and to self
assembled monolayers [24]. The geminal-twin-tails, when
in proximity, appear to reinforce each other in a process called
‘‘adlineation’’ by Shafrin and Zisman [25]. Gladysz, in
extensive recent studies, has expanded greatly the range of
fluorophilic compounds, and finds the ‘‘branched pony tail’’
compounds to be readily synthesized and more highly fluor-
ophilic than non-geminal, in certain cases [17]. Just as the
‘‘hydophilic/lipophilic’’ balance of hydrocarbon surfactants
is an important property, it may well be that the ‘‘fluorophilic/
hydrophilic/lipophilic balance’’ in the more complex long RF
chain segmented alkanoic acids, and other polar compounds,
will play an important role in their selection for specific
purposes. When adsorbedonsurfaces, either smooth orrough,
e.g., paper or fabric, the geminal-twin-tail posphate ester
[CF3(CF2)6–9(CH2)2O]2PO(ONH4) produces a highly oil
repellent surface. Tests show that the twin-tail bis-compound
is immensely more effective than the mono- or tris-phospate
esters [26]. Similarly, twin-tail, long RF chain diesters (suc-
cinate, citrate, et al.) provide a very effective soil repellent
coating on paper or textiles, and have found a large market in
the treatment of carpets [27]. In view of the facile synthesis of
twin-tail acid 13, other geminal-twin-tail derivatives incor-
Scheme 3. Pathways to linear and cyclic adducts from RFCH2CH2SH (6)
and 1,6-alkadienes (2, 10, and 14) by free radical reactions at 70 8C.
2.3. Reaction of equimolar 6 and 2,2-bis-(2-
propenyl)ethanoic acid (10) at 70 8C; conversion to mono
adduct (11) and cyclic adducts (12a,b)
Schemes 3 and 4 illustrate the reaction of 6 (RF ¼ C8)
with 10, Y1 ¼ H and Y2 ¼ CO2H. In Scheme 4, at mol 6/10
¼ one and reaction for 9.5 h at 70 8C (AIBN), the reaction
follows steps (1 and 2) to yield mono-adduct (11), and steps
(3 and 4) to give cyclic adducts (12a,b), in a ratio 11/12a,b ¼
0.370 at 98.1% conversion. Similar reaction of 6 (RF ¼ C6)
with 2 in Table 3 gives a linear/cyclic ratio of 11.3 (AIBN;
1.0 h at 70 8C). Though reaction time and the RF-chain
length of 6 differ, it is probable that the 4-carboxy group
substitution in acid 10 favors the cyclization step (3) for
entropy and steric reasons. Additional discussion of radical
cyclization parameters is given in Section 2.3.1.
Table 4
Effects of thiol 6 concentration, or of mol [6/2], on the reaction of 6 with
1,6-heptadiene (2) at 70.0 8C; percent conversion and isomer ratioa
Entry no.
[6]a
Mol 6/2b
Conversion
(%)c
Mol
(7 þ 9/8a,b)
1
2
3
4
5
6
1.73
0.930
0.505
0.495
0.258
0.258
0.258
51.7
73.3
92.5
20.6
24.4
72.2
13.3
6.33
5.98
2.21
2.19
1.68
1.26
1.22
0.947
0.947
0.947
a See Section 3.2.1 and Table 7 (below) for complete results. Thiol 6 is
n-C6F13CH2CH2SH. Plotting [7 þ 9]/[8a,b] as y, and [6] as x, gives a
straight line for the equation: [7 þ 9]/[8a,b] ¼ (kd1/kc)[6] þ a (intercept;
see Scheme 3). Least squares analysis gives b (intercept of y) ¼ À11.6
(where [6] approaches zero); (kd1/kc) ¼ 14.4; and correlation (r) ¼ 0.999.
b The mol 6/2 is plotted against [7 þ 9]/[8a,b]. Least squares gives
slope ¼ 16:8 and intercept ¼ À2.29; r ¼ 0:999.
c The conversion to 9 is calcd from mols of 9/6, times two. The total
percent conversion is calcd as mols of 7, 8a,b and 9 divided by mol 6 times
100.

N.O. Brace / Journal of Fluorine Chemistry 126 (2005) 7–15
11
Table 5
Reaction products from thiol 6 (C6) and diester 14 at 70.0 8C, 23 h, with
AIBN initiator
Entry no. Substance no. GC, rt (min)b
Sample, relative area (%)
(1)c (2)d
0.663 0.548
1
18
15
18.96
20.54
20.73
20.96
21.42
2
3e
5.51
1.13
5.98
1.24
Regio of 15
Trans-16b
Cis-16a
4
18.0
74.2
0.586
18.5
73.1
0.618
5
6f
Isomer of 16 21.62
Capillary GC and MS/GC analysisa.
a See Section 3.2.7 for reaction conditions and analyses. Thiol 6 is n-
C6F13CH2CH2SH.
b Retention time in min, on DB-1 and DB-5 capillary columns with
Perkin–Elmer GC 3400 instrument.
c Sample (1) contains 6 (1.14%), 14 (0.348%) and 18 (0.663%),
besides the substances (97.8% total) listed. The linear/cyclic ratio (15/
16a,b) is calcd using combined regio isomer and either 15 or 16a,b. This
ratio is 0.0716.
d Sample (2) is taken from the distilled fraction (2).
e This substance is probably a regio isomer of 15; MS/GC give
m=z ¼ 640. See Scheme 5.
Scheme 5. Radical addition of thiol 6 to ethyl bis-(2-propenyl)malonate.
f Possibly a regio isomer of 16a,b, or the corresponding six membered
ring isomer; m=z ¼ 640.
according to Scheme 3. This ratio falls from 11.3 with 2 in
entry 1, to 0.370 in reaction with 10 in entry 2, and to 0.0782
for reaction with 14 (or, 30.5:5:2:1). In an extended chain
form, the 4-substituted-heptadiene molecule has serious
non-bonded interactions of the 4-carboxy, or the 4,4-car-
boethoxy groups, with the adjacent carbon atoms. This
affects the distribution of molecular conformations, favoring
those with a minimum of gauche interactions, and is an
example of the Thorpe–Ingold effect [28]. With a smaller
number of conformations, the transition state that leads to a
ring closed product causes the lowering of activation entropy
[29]. An argument from thermodynamic principles is less
porating the long chain RF(CH2)nS moiety wouldlikelyafford
new opportunities for synthesis and novel applications.
2.4. Free radical reaction of thiol 6 with ethyl 2,2-bis-(2-
propenyl)-1,3-propanedioate (14); conversion to linear
adduct 15 and cyclic adducts 16a,b
As in Section 2.3 above, equimolar thiol 6 (C6) and
diester 14 react at 70.0 8C, for 23 h (AIBN, 1.5 mol%) to
give combined adducts 15-16a,b in 98.7% yield (Table 5;
Scheme 5). There is none of the bis-adduct, 17, in the
1
mixture. H and 13C NMR, COSY plots, NOE irradiation
experiments, and MS fragmentation patterns combine to
establish the structures of 16a (cis) and 16b (trans); see
Fig. 1. The linear/cyclic adduct ratio is 0.0176, and the cis/
trans ratio of 16a,b is 4.2.
A side product is 7,7-bis-ethoxycarbonyl [3.3.0] bicyclo-3-
thiaoctane (18), m=z ¼ 272, and its origin from 16 is sug-
gested in Scheme 6. The radical 16 cyclizes to an unstable,
quasi-sulfurane radical 21 (sulfur has nine electrons), which
expels RFCH2CH2 (22), and converts to the thiophane 18. The
radical 22 may dimerize, or abstract an hydrogen atom.
However, radical 22 initiates a new radical chain in unpub-
lishedwork[9]. Radical22addsto14, followedbycyclization
to radical 24 (step 4), and it abstracts an hydrogen from 6 (step
5) to form the sulfur-free adduct 24 and radical 6.
2.5. Summary of thiol 6, and comparison with RFI, in
radical addition to 2 and to 4-substituted-1,6-heptadienes
Fig. 1. Stereochemical structures of cis and trans isomers 16a and 16b; 1H
NMR, COSY, NOE, and MS results.
Table 6 summarizes the effect of 4-substitution in 2, 10,
and 14, in reaction with 6, on the linear to cyclic adduct ratio

12
N.O. Brace / Journal of Fluorine Chemistry 126 (2005) 7–15
3. Experimental section
3.1. Source of materials and physical methods
3.1.1. Preparation and properties of materials
Thiols 6, RFCH2CH2SH, RF ¼ n-C6F13 and n-C8F17, are
prepared as in [20,22]. Redistilled in column A, 6 (n-C6F13),
bp 67.5–68.0 8C/25 mm, 99.3% C6 by GC, and (n-C8F17),
bp 84.0 8C/14 mm, 98.6% C8 by GC, are transferred under
nitrogen from a sealed bottle to the reaction set up. 1H NMR
(thiol 6, n-C8F17): d 1.09, t, 1H, H-1, exchanges slowly with
D2O; d 1.85–3.06, m, 4 H, H-2, H-3. Other substances are
purchased as needed. Compounds 10, 14, and 2,2-bis-(2-
propenyl)-1,3-propanedioic acid (19) are prepared in
improved yield by methods adapted from the literature,
which are described in detail in Sections 3.2.1–3.2.3.
Scheme 6. Cyclization and fragmentation of thiol adduct radical 16;
formation of 7,7-bis-ethoxycarbonyl[3.3.0]bicyclo-3-thiaoctane (18); addi-
tion of radical 22 to 14, cyclization to thio-free analogue 24.
3.1.2. Physical methods
Samples for 1H NMR are dissolved in DCCl3, unless
otherwise indicated, and are run at 100, 200, and 500 MHZ.
13C NMR are run at 80 MHz. NMR and elemental analyses
are provided through the courtesy of Ciba–Geigy Analytical
Research Division at Ardsley, NY, and are satisfactory for
each pure substance. A 3 ft, stainless steel spinning band
column (Nester–Faust) is column A; a 24 in. Teflon1 spin-
ning band column is column B. Capillary GC analyses are
run on a Perkin–Elmer 3400 instrument with automated area
calculations.
applicable, since the transition state is closer in energy to the
open chain form than to the cyclized, more stable form of the
molecule [8,30]. Thus, the reaction is controlled by the
kinetic and not thermodynamic factors. The adduct radical,
11 (Scheme 4), or radical 15 (Scheme 5), readily assumes a
conformation with the non-bonded electron (SUMO) lying
close to the p-bond (LUMO) of the propenyl group
[8,31,32].
For the reactions of RFI and the same 4-substituted-1,6-
heptadienes (Table 2), the results are in good accord with
those from thiol 6, as the linear/cyclic ratio decreases in the
same order. The actual values differ, as the kinetic ratio,
ðkd1=kcÞ ¼ 0:568 for RFI with 2, is 25 times smaller than that
of 6 (kd1=kc ¼ 14:4 at 70 8C); and, the reaction conditions
and mol ratio of reactants differ. For the case of extended
reaction times as in Table 2 (21 or 24 h), the experimental
linear/cyclic ratio is 2.78 at [RFI] ¼ 4.81, while the calcd
linear/cyclic ratio from the equation of Section 1.1, is 2.61.
However, after 24 h of reaction, the experimental linear/
cyclic ratio for reaction at 60 8C is 1.17, and this value is not
far from the expected [7].
3.2. Experimental procedures
3.2.1. Reaction of thiol 6 with 1,6-heptadiene (2) at 70.0
8C; Conversion of 2 to 10-(perfluorohexyl)-8-thia-1-decene
(7), cis- and trans-1-methyl-2-[4-(perfluorohexyl)-2-
thiapropyl]-cyclopentane (8a,b), and 1,13-bis-
(perfluorohexyl)-3,11-(bis-thia)tridecane (9)
A heavy wall glass reactor tube with small magnet stirring
bar is charged with 6 (n-C6F13; 1.685 g, 4.432 mmol), and
AIBN (0.0761 g, 1.25 mmol). A mixture of 1-hexene
(0.4013 g, 4.768 mmol; internal reference), 1,6-heptadiene
(2, 0.4583 g, 4.766 mmol) and 1,2-dichlorobenzene
Table 6
The effect of 4,4-geminal substitution on the linear/cyclic adduct mol ratio in the addition of thiol 6 to 10 and to 14, in comparison with unsubstituted 2a
Entry
no.
Thiol (6),
RF
(CH2¼CHCH2)2CY1Y2
6/x-hpdb
(mol/mol)
Time/temp
(h/8C)
Total yield
(%)
Linear/cyclic adducts
No.
Y1
Y2
1c
2d
3e
C6F13
C8F17
C6F13
2
10
14
H
H
0.964
1.00
1/70
9.5/70
23/70
95.4
98.1
97.7
11.3
H
CO2H
CO2Et
0.299
0.0716
CO2Et
0.997
a See Tables 3, 5 and 7, and Sections 3.2.1, 3.2.5 and 3.2.7 for details. Substances used are 2, 4-carboxy-1,6-heptadiene (10), and 4,4-bis-ethoxycarbonyl-
1,6-heptadiene (14).
b The mol ratio of thiol 6 over the (substituted) 1,6-heptadiene.
c See Tables 3 and 7 and Section 3.2.1.
d Section 3.2.5.
e Section 3.2.7 and Table 5.

N.O. Brace / Journal of Fluorine Chemistry 126 (2005) 7–15
13
Table 7
Effect of thiol (6) concentration on linear/cyclic adduct ratio [7 þ 9]/[8a,b] in reaction with 1,6-heptadiene (2) at 70.0 8Ca
Entry no.
Time (min)
Reactants
Conversion (%)b
Products (mmol)
Linear/cyclic adductsa
[7 þ 9]/[8a,b]
[6/2]
[6]
6
7
8a,b
9
1c
2c
3c
4
2.0
7.00
20
0.929
0.929
0.929
0.838
0.505
0.495
0.258
0.258
0.258
0.258
1.73
51.7
64.6
71.0
57.0
73.3
92.5
20.6
24.6
72.4
94.1
1.73
0.143
0.236
0.310
0.137
0.235
0.303
0.0921
0.110
0.382
0.564
0.209
0.310
0.358
0.0980
0.114
0.147
15.1
11.1
9.15
7.60
6.82
6.47
2.21
2.19
1.71
1.39
1.73
1.73
2.01
2.12
15
1.37
0.845
1.37
1.67
5
15
30
1.26
1.22
6
7d
6d
9e
10e
60
0.947
0.947
0.947
0.947
0.203
0.241
0.629
0.752
–
d
d
120
60
–
0.0121
0.0152
120
a Thiol 6 is n-C6F13CH2CH2SH. See also Tables 3 and 4. In calculating conversion of 6 to 9, the amount of 9 mmol is multiplied by two to show the actual
consumption of 6. Thus, [7 þ (9 ꢀ 2)/8a,b] mmol is the quantity given in the table.
b The percent conversion of 6 to 8a,b is calcd as 8a,b/[total (7 þ 8a,b) þ (9 ꢀ 2)] mol times 100.
c The linear/cyclic adduct ratio ¼ 11.3 after 60 min reaction of 6 and 2 (6/2 ¼ 0.964) in Table 3. However, the concentration of 6 is 2.34 M. which is 1.35
times greater than in runs 1–3 above. Hence, the increase in the ratio is reasonable.
d Air is introduced to the reaction of 6 and 2, which greatly retards the rate; the amount of bis adduct is too small to measure accurately by GC.
e Air is purged from the reaction tube, and rapid reaction occurs. After 60 min, 72.4% conversion of 6 and after 120 min, 94.1% conversion.
(0.3641 g, internal reference) is prepared (total volume is
2.562 mL). Then, 0.0110 g (3:76 ꢀ 10À3 part) is removed,
and one drop added to 0.10 mL of acetone for GC response
factors (capillary DB-5, 30 m). The mixture is pipetted into
the reactor tube, which is cooled to À196 8C, evacuated and
filled with nitrogen three times, and sealed. The tube is
heated at 70.0 8C for 0.25 h. A GC sample (1; 0.005 mL) is
removed by syringe, and diluted with 0.10 mL of acetone.
Making use of FID values for 2, 7, 8a,b and 9, the mol
amount of each substance in the reaction mixture is deter-
mined. The physical properties and 1H NMR of each
compound are previously reported [22]. This procedure
is followed for subsequent samples listed in Tables 4
and 7.
3.2.3. Hydrolysis of 14 to 2,2-bis-(2-propenyl)-1,3-
propanedioic acid (19)
A 500 mL flask, set up as in Section 3.2.2, is charged with
KOH (33.7 g, 0.60 mol; dissolved in water, 100 mL), etha-
nol (100 mL) and 14 (redistilled, 48.0 g, 0.20 mol). The
mixture is stirred and heated for six h (80 8C, reflux).
Ethanol (100 mL) is distilled, the clear mixture acidified
with HCl (2 ꢀ 75 mL, 6N; 1.6 mol), and diacid 19 is
extracted with diethyl ether (50, 3 ꢀ 25 mL). The ether is
boiled off (steam bath) and 19 is dissolved in benzene
(200 mL). When cool, 19 crystallizes, 33.6 g, 91.2% con-
version, mp 135–136 8C (gas). The filtrate is evaporated to
ca. 25 mL, and cooled to give 19, 1.0 g, mp 132–134 8C
(gas); total conversion of 93.5% (lit: mp 135–137 8C) [35].
3.2.2. Ethyl 2,2-bis-(2-propenyl)-1,3-propanedioate (14)
The procedure of Organic Syntheses is adapted to the bis-
ester, 14 [33]. Ethyl malonate (82.5 g, redistilled;
0.515 mol) and ethanol (350 mL, anhydrous, distilled from
Mg(OCH3)2 into the flask) is stirred by a paddle stirrer while
sodium (1.00 mol; fresh cut under toluene) is added during
one h. Additional ethanol (100 mL) is added to the thick
slurry of the enolate salt (basic). 1-Bromo-2-propene
(121.0 g, 1.00 mol; redistilled) is added dropwise (1 h)
and stirring continued for 3 h at reflux temperature (mixture
is neutral in pH). At the water pump (Claisen head), alcohol
distills (ca. 400 mL) up to Tpot150 8C, water (200 mL) is
added, and the water layer is washed with benzene (50 mL).
Distillation (column A) gives: (1) bp 117–125 8C/15 mm,
3.2.4. Decarboxylation of 19 to 2,2-bis-(2-
propenyl)ethanoic acid (10)
The diacid 19 (34.0 g, 0.187 mol) in a 100 mL distillation
flask, with a total reflux, partial take-off-head, is heated and
stirred (in an oil bath, by a magnet bar), and the pressure
reduced to 20 mm. Distillation of 10 (and gas evolution)
begins at ca. 154 8C (oil bath) and continues at 135–
140 8C for 3 h, bp 124 8C/20 mm, n25 1.4500; 25.0 g,
D
95.7% yield. IR confirms the structure of 10; lit: bp
113 8C/11 mm, n20D 1.4510 [36,37].
Anal calcd for C8H12O: C, 68.5; H, 8.63. Found: C, 68.5;
H, 8.78.
3.2.5. Thiol 6 (C8) and 2,2-bis-2-(propenyl)ethanoic acid
(10) (mols 6:10 ¼ 1.00) yield [8-(perfluorooctyl)-6-thia]-
2(2-propenyl)octanoic (11) and cis- and trans-3-methyl-4-
[4-(perfluorooctyl)2-thiabutyl]-1-cyclopentanoic acid
(12a,b)
27.9 g, n25D 1.4400; (2) bp 125–128 8C/15 mm, 41.5 g, n25
D
1.4432; and (3) diester 14, bp 128–125 8C/15 mm, 31.9 g,
n25 1.4446. Fractions (1) and (2) contain ethyl-2-prope-
D
nylmalonate (7%) and 14 (79%; lit: bp 113 8C/11 mm, n20
1.4468) [34]. Two successive distillations (column B) pro-
D
A heavy wall, glass reactor tube (Fischer–Porter aerosol
tube) is charged with a small stirring magnet, 6 (24.0 g,
vide pure 14, bp 131 8C/15 mm, n25 1.4437.
D

14
N.O. Brace / Journal of Fluorine Chemistry 126 (2005) 7–15
0.0500 mol, 2.20 M), 10 (7.00 g, 0.0500 mol, 2.20 M), and
AIBN (0.164 g, 1.00 mmol; 2.0 wt.%), the tube cooled to
À78 8C, evacuated and filled with nitrogen three times, and
sealed. The tube is heated in an oil bath, also stirred by a
magnet bar, at 70.0 8C for 9.5 h. The viscous, clear mixture
is transferred, with the aid of ether, to column A (100 mL
distillation flask), ether is removed and the pressure reduced
to 10 mm but nothing distills. Further pumping at 0.40 mm
(hivac pump) for 10 min gives a small amount of sublimed
solid (probably tetramethylsuccinonitrile, from AIBN) in
the distillation head. The residual oil mixture of 11 and
12a,b (30.49 g, 98.1% conversion) is solid when cold, but
melts at 25 8C on a Hirsch funnel; mols 11:12a,b ¼ 27:73
(NMR). 1H NMR: d 0.90, m, 2.2 H, CH3-CH in 12a,b, cis/
trans ¼ ca. 4.0 (73.3% of total); d 1.7, m, 3.5 H,
CH2¼CHCH2 in 11 and two ring CH2 in 12a,b; d 2.0–
3.0, m, 9.4 H, RFCH2CH2S(CH2)3 in 11 and
RFCH2CH2S(CH2) in 16a,b; d 5.05, 0.55 H, s, d, CH2¼CH
in 11 (27% of product); d5.72, m, 0.28 H, CH2¼CH of 11
(27% of product). IR: v 3080, CH of CH2¼CH (weak); v
33002600, bonded COOH; v 1700, C¼O(st); v 1640,
CH2¼CH (weak); v 1280-1140 cmÀ1, CF bands. Elemental
anal agrees with a mixture of 11 and 12a,b.
Anal calcd for C28H22F34S2O2: C, 30.5; H, 2.01; F, 58.7.
Found: C, 30.9; H, 1.91; F, 58.9.
3.2.7. Thiol 6 (C6) and ethyl 2,2-bis-(2-propenyl)-1,3-
propanedioate (14) yield ethyl 2-[6-(perfluorohexyl)-4-
thiahexyl]-2-(2-propenyl)-1,3-propanedioate (15), and
ethyl cis- and trans-3-methyl-4-[4-(perfluorohexyl)-2-
thiabutyl]-cyclopentan-1,1-bis-carboxylate (16a; 16b)
As in Section 3.2.5, a heavy wall, glass pressure tube
(Fischer–Porter) is charged with thiol 6 (C6; 3.814 g;
10.03 mmol), ester 14 (2.415 g, 10.06 mmol; GC,
98.87%); AIBN (0.0250 g; 0.152 mmol); and benzene
(0.50 mL, used to rinse weighing vial and funnel). The tube
is cooled to À10 8C, evacuated and filled with nitrogen three
times and sealed. The reaction mixture is stirred by magnet
bar at 70:0 þ = À 1 8C (oil bath) for 23 h, cooled to 25 8C
(remove sample no. 1), rinsed with benzene into a flask, and
distilled, without a column, using a total reflux, partial take-
off-head. Benzene is removed to a cold trap at the water
pump, and heating is continued to 190 8C/12 mm. The
residual oil weighs 6.00 g. Fractions are taken at reduced
pressure: (1), bp 128–150 8C/0.70 mm, 0.51 g; (2), bp 155–
156 8C/0.50–0.30 mm, 4.14 g; and (3), bp 152–155 8C/
0.35 mm, 0.99 g; residual oil, 0.18 g. The dry ice cooled
trap is empty. The reaction tube is rinsed with acetone, and
evaporation affords 0.1347 g; total mass recovered is
6.173 g (98.7%). GC (capillary GC; see Table 5; sample
1): 6, 1.142%; 14, 0.348%; 18, 0.66%; combined 15–16a,b,
97.8%. The relative areas of products are recorded in Table 5.
The bis-adduct, ethyl 2,2-bis-[6-(perfluorohexyl)-4-thia-
hexyl]-1,3-propandioate (17) is not found in the product
mixture.
Anal calcd for C18H17F17O2S: C, 34.8; H, 2.92; F, 52.0.
Found: C, 34.7; H, 2.69; F, 51.8.
3.2.6. Metered addition of 2,2-bis-2-(propenyl)ethanoic
acid (10) to a large excess of thiol 6 (C8) yields 2,2-bis-[6-
(perfluorooctyl)-4-thiahexyl]ethanoic acid (13)
The set up of 3.2.4 is modified to include a ‘‘Varibor’’
(needle valve) dropping funnel with side arm connected to a
nitrogen feed, controlled by a leveling oil trap; and vented
through a À78 8C cold trap; the mixture is stirred by a
magnet bar. Thiol 6 (RF ¼ C8, 97.2%, C10, 1.6%; 48.0 g,
0.100 mol) and AIBN (0.164 g, 1.00 mmol) are charged to
the flask and heated to 67 8C (oil bath). Diacid 10 (3.50 g,
0.0250 mol; 3.85 mL, d ¼ 0:91) is added drop wise during
40 min (0.096 mL/min; 0.624 mmol/min) while stirring at
70 8C (bath, 72 8C). After 30 min, and ca. 3.0 mL (calcd,
2.9 mL) of 10 is added, an exotherm to 79 8C occurs; the
flask is cooled momentarily, and heating continued for 6.5 h
at 70 8C. White solid 13 forms upon cooling. At the water
pump, excess 6 distills, bp 80 8C/9.0 mm, n25D1.3320,
25.5 g, (53.1 mmol, thus, 46.9 mmol of 6 is consumed,
93.8% conversion), leaving 13 (25.3 g, 22.9 mmol, 91.6%
conversion, 97.7% yield on 6), mp 62–72 8C. TLC of 13, one
major and two trace impurities (probably 11 and 12a,b).
Diacid 13 is recrystallized from ligroine (bp 60–90 8C), mp
81–82 8C; TLC, one major spot and one trace impurity. IR
(both samples): v C¼O of COOH, 1699 (s), d CH, 1460,
1430, 1370, 1335; v CF, 1250–1200 (very strong); heavy
Anal calcd for C21H25F13O4S: C, 40.6; H, 4.06; F, 39.8; S,
5.17. Found (fraction 2): C, 40.6; H, 4.1; F, 39.5; S, 4.8.
3.2.8. NMR and GC/MS analysis of adducts 15-16a,b;
see Fig. 1
Samples 15–16a,b (distilled fraction 2) is examined by
high resolution NMR (XL-500) in CDCl3 solution with the
assistance of Dr. Ronald Rodebaugh. 1H NMR spectra reveal
a mixture of principally mono-adduct 15 (7.4%), cis-16a
(74.1%) and trans-16,b (18.5%); integrated areas of 16a and
16b, are 168 and 40, respectively, or in a 4:2 ratio. 1H NMR:
d 0.85, d, 74.1%, 16a; d 1.1, d, 18.5%, 16b; d 1.2–1.5, m,
CH3CH2O; d 1.68–1.75, complex m, CHa and CHb of 16b; d
2.16–2.28, complex m, CHa and CHb of 16a; d 2.0, d ꢀ d,
CH2 at positions 2 and 5 of the cyclopentane ring in 16a; d
2.6, d ꢀ d, CH2 at positions 2 and 5 in 16b; d 2.3–2.4,
complex m, RFCH2CH2S, CH coupled to CF; d 2.70–2.74,
an approximate triplet, RFCH2CH2S, CH2 next to sulfur; d
4.17, q, CH3CH2O; d 4.8–5.15, m, CH2¼ of 15; d 5.59, m,
CH¼ of 15. The key observation stems from the effect of
irradiation on the methyl doublet (CH3 [a]) of the cis and
trans-16a and 16b. An enhanced NOE intensity of only the
Hb, but not that of HC resonance, occurs in the cis-16a. In the
trans-16b, irradiation of the CH3[a] doublet gives enhanced
bands at 1115, 1080, 1030, 995, 950, and 700 cmÀ1. H
1
NMR: (None of 6 or 10 are present; impure 13 contains a
trace of 12a,b, from a weak signal at d 1.0 for CH3CH, and
this is absent in pure 13). d 1.6, m, 8 H, (-CH2CH2)2C-; d
2.0–3.0, 13 H, (RFCH2CH2SCH2-)2; d 11.5, 1 H, COOH.

N.O. Brace / Journal of Fluorine Chemistry 126 (2005) 7–15
15
[12] N.O. Brace, Ethyl-3-perfluoroalkyl-2-iodopropylmalonate from ethyl
allylmalonate, J. Org. Chem. 40 (1975) 851.
NOE signals for both of the geminal Hb and the vicinal HC
signals. This is consistent with CH3[a] geminal to Hb and cis
to HC in 16b, and with CH3[a] geminal to Hb and trans to HC
in 16a. This defines the stereochemistry of 16b as trans with
respect to CH3[a], and the RFCH2CH2S moieties; and cis
with respect to those same moieties in 16a.
[13] K.C. Smeltz, US Patent 3,478,116 March, 1969.
[14] K.C. Smeltz, US Patent 3,504,016 March, 1970.
[15] J.M. Vincent, A. Rabion, V.K. Yachandra, R.H. Fish, Fluorous
Biphasic Catalysis: Complexation of 1,4,7-[C8F17(CH2)3]3-1,4,7-
Triazacyclononoane with [M(C8F17(CH2)2CO2)2] (m¼Mn,Co) to
provide Perluoroheptane-Soluble Catalysts for Alkane and Alkene
Functionalization in the presence on t-Bu OOH and O2. Angew.
Chem. Int. Ed. Engl. 36 1997) 2346.
GC/MS: a 15 m, DB-5 capillary column is heated from 40
to 300 8C, at the rate of 10 8C/min. The first peak eluted is
identified as 7,7-bis-ethoxy-carbonyl-[3.3.0]-bicyclo-3-
thiaoctane (18) from its molecular ion m=z ¼ 272, its frag-
mentation pattern, and the presence of an M þ 2 ion,
m=z ¼ 274; this indicates that a sulfur isotope is present.
[16] J. Loiseau, E. Fouquet, R.H. Fish, J.-M. Vincent, J.-B. Verlhac, A
new carboxylic acid with branched pony tails for the solubilization of
Mn(11) and Co(11) ions in perfluorocarbons, J. Fluorine Chem. 108
(2001) 195.
[17] M. Wende, F. Seidel, J.A. Gladysz, See leading references to
branched pony tails, J. Fluorine Chem. 124 (2003) 45–54.
[18] N.O. Brace, RF(CH2)3OH by four methods, up to 93% conversion
(RF ¼ n-C4F9 to n-C8F17), J. Fluorine Chem. 20 (1982) 313.
[19] N.O. Brace, L.W. Marshall, C.J. Pinson, G. van Wingerden,
CF3(CF2)5(CH2)3I (72% conversion) from CF3(CF2)5(CH2)3OH, J.
Org. Chem. 49 (1984) 2361.
1
The H NMR of 18 is devoid of vinyl protons. The 15 and
16a,b adducts in MS/GC have characteristic fragmentation
patterns, and the mol ion, m=z ¼ 620, as do the two
unknowns. They are, therefore, isomers of 15 and 16a,b;
possibly, regioisomers or the corresponding cis and trans-
cyclohexane adducts. The amounts are too small to be
identified by NMR.
[20] N.O. Brace, RF(CH2)nSH (n ¼1–12) gives RF(CH2)nS(alkylene)Y,
Y ¼ COOH, CN, and NH2; preparation and reactions, US Patent
3,172,910, 9 March 9 1965. Chem. Abstr., 63, 1965, p. 503c.
[21] N.O. Brace, S.G. Mull, 3-(Perfluoroalkylethanethio)alkylsuccinic acids
RS(CH2)3CH(CO2H)CH2COOH), and, derived amic acids, imides,
esters, and salts. See also for leading references to RF-surfactants and to
measurement of surface activity, J. Fluorine Chem. 121 (2003) 33–50.
[22] N.O. Brace, RF(CH2)nSH (n ¼ 2) preparation and radical addition to
alkenes, cycloalkenes, alkadienes and alkynes (21 different com-
pounds), J. Fluorine Chem. 62 (1993) 217.
Acknowledgements
It is a pleasure to acknowledge assistance by Dr. Ronald
Rodebaugh in the acquisition and interpretation of NMR
data. I thank Mr. B. Piatek for assistance in obtaining GC/
MS data, to aid in ascertaining the structures of the products
of Tables 4 and 5.
[23] N.O. Brace, A review of RF(CH2)nSH preparation and reactions, with
extensive references to radical reactions in Section 8, J. Fluorine
Chem. 108 (2001) 147–175.
[24] J.G. Riess, A Review. Perfluoroalkyl-substituted surfactants, blood
substitutes, and related substances ca. 2000 refs, Chem. Rev. 101
(2001) 59–65.
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