Synthesis and properties of ABA amphiphiles

Full text of DOI:10.1021/jo990620m

6870
J . Org. Chem. 1999, 64, 6870-6873
Notes
Sch em e 1
Syn th esis a n d P r op er ties of ABA
Am p h ip h iles
Yiyan Chen and Gregory L. Baker*
Department of Chemistry and Center for Fundamental
Materials Research, Michigan State University,
East Lansing, Michigan 48824
Received April 13, 1999
Neutral amphiphilic molecules have a broad range of
applications ranging from nonionic surfactants1,2 to
templates for the synthesis ofporous inorganicmaterials.3-9
Some of the simplest and most versatile surfactants are
combinations of linear alkyl and poly(ethylene glycol)
(PEG) segments in an AB or ABA pattern, where A
represents the alkyl portion and B corresponds to the
PEG segment. We are particularly interested in am-
phiphilic molecules that have an ABA structure because
they self-assemble to give ordered solid-state materi-
als10,11 and serve as models for understanding the ion-
molecule complexes that are found in polymer electro-
lytes.12 ABA amphiphiles also are important models for
a series of recently synthesized (AB)n microblock copoly-
mers.13,14 A number of ABA surfactants are known, but
it would be helpful to have a more complete series of ABA
compounds so the trends in properties could be mapped
in detail and related to those seen in polymers. To that
end, we synthesized and characterized several families
of ABA amphiphiles, and we report here their synthesis
and some of their physical properties.
available, and thus the main synthetic challenge is
obtaining the exact-length PEGs needed for the desired
ABA structures. PEGs are commercially available in a
variety of molecular weights, but only a limited number
of exact-length glycols are available in high purity.
Chromatographic separation of glycols from commercially
available PEG mixtures was considered, but to ensure
the purity of the glycols in the amounts needed (tens of
grams), we opted for an iterative synthetic approach that
allowed us to access a broad range of PEG lengths on
large scales.
For ABA amphiphiles to be useful models for (AB)n
microblock copolymers, they must replicate the solution-
and solid-state properties of the polymers. Because the
physical properties of the polymers are sensitive to
distributions in the lengths of the blocks, we needed to
prepare ABA model compounds where the length of each
block was exact. Exact length alkyl segments are readily
Resu lts a n d Discu ssion
With the increased interest in using PEGs in polymer-
supported solid-phase synthesis, cyclic ethers, and as
elements of new materials, there have been several
reports describing the synthesis of exact length PEGs.
We adopted a modified version of the approach of
Keegstra et al.15 to prepare glycols where y is 6-10 and
14. The route to these PEGs is outlined in Scheme 1.
Success in any iterative synthesis demands that each
step proceeds in high yield and that each intermediate
be readily purified. Our work incorporated modified
workup protocols designed to simplify product isolation
and minimize the need for chlorinated solvents. For the
preparation of the ditosylates, we used aqueous KOH
instead of the powdered KOH/CH2Cl2 mixture used by
Keegstra. We found the aqueous system easier to handle,
and in our hands, it gave purer products. In addition,
we noted that the conditions used by Keegstra (dry CH2-
Cl2/KOH) are very similar to those used for preparing
(1) Chu, B.; Zhou, Z. In Nonionic Surfactants: Polyoxyalkylene Block
Copolymers; Nace, V. M., Ed.; Surface Science Series; Marcel Dekker:
New York, 1996; Vol. 60.
(2) Sjoblom, J .; Stenius, P.; Danielsson, I. In Nonionic Surfactants:
Physical Chemistry; Nace, V. M., Ed.; Surface Science Series; Marcel
Dekker: New York, 1987; Vol. 23.
(3) Tanev, P. T.; Pinnavaia, T. J . Science 1996, 271, 1267-1269.
(4) Braun, P. V.; Osenar, P.; Stupp, S. I. Nature 1996, 380, 325-
328.
(5) Eftekharzadeh, S.; Stupp, S. I. Chem. Mater. 1997, 9, 2059-
2065.
(6) Goltner, C. G.; Henke, S.; Weissenberger, M. C.; Antonietti, M.
Angew. Chem., Int. Ed. Engl. 1998, 37, 613-616.
(7) Zhao, D. Y.; Huo, Q. S.; Feng, J . L.; Chmelka, B. F.; Stucky, G.
D. J . Am. Chem. Soc. 1998, 120, 6024-6036.
(8) Raimondi, M. E.; Marchese, L.; Gianotti, E.; Maschmeyer, T.;
Seddon, J . M.; Coluccia, S. Chem. Commun. 1999, 87-88.
(9) Goltner, C. G.; Berton, B.; Kramer, E.; Antonietti, M. Chem.
Commun. 1998, 2287-2288.
(10) Matsuura, H.; Fukuhara, K. J . Phys. Chem. 1987, 91, 6139-
6148.
(11) Matsuura, H.; Fukuhara, K.; Masatoki, S.; Sakakibara, M. J .
Am. Chem. Soc. 1991, 113, 1193-1202.
(12) Frech, R.; Huang, W. W. Macromolecules 1995, 28, 1246-1251.
(13) Qiao, J .; Chen, Y.; Baker, G. L. Submitted to Macromolecules.
(14) Qiao, J .; Chen, Y.; Baker, G. L. Chem. Mater., in press.
(15) Keegstra, E. M. D.; Zwikker, J . W.; Roest, M. R.; J enneskens,
L. W. J . Org. Chem. 1992, 57, 6678-6680.
10.1021/jo990620m CCC: $18.00 © 1999 American Chemical Society
Published on Web 08/18/1999

Notes
J . Org. Chem., Vol. 64, No. 18, 1999 6871
in the PEG segment, where an odd number of EO units
correspond to an even number of oxygen atoms and a
relatively high melting point. The odd-even effect can
be understood by treating the oxygen atoms in the chain
as defects in a linear alkane caused by the difference in
the C-O-C bond angle relative to that of the C-C-C
bond angle. Assuming the ABA chains adopt a planar
zigzag conformation places successive oxygen atoms anti
to each other, effectively canceling the distortions. Thus,
ABA amphiphiles with odd values of y are more linear
and have higher melting points. Since the odd-even
effect is related to the overall linearity of the amphiphile,
increasing the length of either the alkyl or the ethylene
oxide segments should result in a more linear structure.
For long chains, the distortion introduced by an odd
number of oxygen atoms can be accommodated by small
changes in the conformation of the alkyl and ethylene
oxide segments that restore the overall linear shape of
the amphiphile. As shown in Figure 1, the odd-even
effect becomes weak for x g 12 or y g 6.
Exp er im en ta l Section
F igu r e 1. Melting points of CxEOyCx amphiphiles. The
numbers in the inset are the values of x for the compounds.
The melting points were measured under helium by dif-
ferential scanning calorimetry at a rate of 10 °C/min.
P r ep a r a tion of Oligom er ic Eth ylen e Glycol Ditosyla tes,
1,5-Bis(tosyloxy)-3-oxa p en ta n e [Ts(OCH2CH2)2OTs, 2(2)].
A solution of diethylene glycol (130 g, 1.22 mol) and p-toluene-
sulfonyl chloride (701 g, 3.66 mol) in THF (1.5 L) was placed in
a 3 L three-necked round-bottom flask and stirred with a
mechanical stirrer. The flask was cooled with an ice/water bath,
and a solution of KOH (450 g, 8.00 mol) in water (500 mL) was
added slowly over a period of 1 h. The ice-water bath was
removed, and the system was stirred for an additional 7 h. The
resulting suspension was poured into a mixture of 1 L of CH2-
Cl2 and 500 mL of ice-water, and the aqueous layer was
extracted with CH2Cl2. The combined organic solutions were
washed three times with distilled water and dried over MgSO4
overnight. After removal of MgSO4 and solvent, the solid was
recrystallized twice from methanol to give 89% yield of 2(2) as
a white crystalline product: 1H NMR (300 MHz, CDCl3) δ 7.76
(d, 4H), 7.33 (d, 4H), 4.07 (t, 4H), 3.59 (t, 4H), 2.43 (s, 6H); mp
87.5-88.5 °C (lit.16 mp 87.0-87.5 °C)
chain-extended poly(ethylene oxide) polymers. By switch-
ing to an aqueous system, we eliminated chain extension
as a potential side reaction. The workup procedure for
the monotritylates was also simplified, enabling us to
obtain pure products in high yield. Both the monotritylate
and ditritylate syntheses were modified to eliminate the
need for CH2Cl2.
The ABA surfactants were prepared by treating the
appropriate glycol with NaH and 2 equiv of the desired
alkyl bromide. Depending on the molecular weight, the
products ranged from viscous oils to waxy solids. Products
with short chain length were initially purified by distil-
lation, and all samples were also purified by low-
temperature crystallization. Because the solubility of the
amphiphiles changes with chain length, the short-chain
compounds (y ) 2, 3) were crystallized from acetone while
the longer chain compounds (y ) 4-8, 10, 14) were
crystallized from methanol.
The melting points for the series of ABA amphiphiles
were measured by differential scanning calorimetry
(DSC), and the results are plotted in Figure 1. For alkyl
groups with x g 10, the melting points of a series of ABA
amphiphiles show a weak dependence on the length of
the PEG segment. In contrast, increasing the length of
the alkyl chain by two carbon atoms shifts the melting
points for a series to higher temperatures. The trend in
melting points is similar to that of the n-alkanes. For
example, the melting points of C8EO7C8 and C10EO7C10
are 9 and 22 °C; the corresponding melting points for C16
and C20 are 18 and 38 °C.
Another feature of the melting point data is the
oscillation of the melting points within a series, especially
when y e 6. ABA molecules with odd values of y have
systematically higher melting points than those where y
is even. Odd-even effects are commonly seen in the
melting points of n-alkanes and molecules such as liquid
crystals, where chromophores or mesogens are linked
with short alkyl chains in a planar zigzag conformation.
In the ABA amphiphiles, the odd-even effect originates
1,8-Bis(t osyloxy)-3,6-d ioxa oct a n e [Ts(OCH 2CH 2)3OTs,
2(3)]. 2(3) was prepared similarly to give 87% yield of a white
crystalline solid. 1H NMR (300 MHz, CDCl3) δ 7.77 (d, 4H), 7.32
(d, 4H), 4.12 (t, 4H), 3.63 (t, 4H), 3.51 (s, 4H), 2.43 (s, 6H). mp
80-81 °C (lit.16 87.0-87.5 °C).
Ditosyla tes for y ) 4-10 [Ts(OCH2CH2)yOTs, 2(y)]. Ditos-
ylates 2(y) for y ) 4-10 were prepared the same way as
diethylene glycol ditosylate. After the reaction was finished, ice-
water was added, the solution was separated, and the aqueous
layer was extracted with diethyl ether. The combined organic
solutions were washed with saturated aqueous NaCl solution
and dried over MgSO4 overnight. After removal of MgSO4 and
solvent, a clear, colorless to light yellow viscous liquid was
obtained. The product was pure enough for further use.
1,11-Bis(tosyloxy)-3,6,9-tr ioxa u n d eca n e [Ts(OCH 2CH2)4-
OTs, 2(4)]. A clear, colorless oil17 was obtained in 99% yield:
1H NMR (300 MHz, CDCl3) δ 7.78 (d, 4H), 7.32 (d, 4H), 4.12 (t,
4H), 3.65 (t, 4H), 3.57 (s, 4H), 3.54 (s, 4H), 2.43 (s, 6H).
1,14-Bis(tosyloxy)-3,6,9,12-tetr aoxatetr adecan e [Ts(OCH2-
CH2)5OTs, 2(5)]. A clear, colorless oil18 was obtained in 99%
yield: 1H NMR (300 MHz, CDCl3) δ 7.78 (d, 4H), 7.32 (d, 4H),
4.12 (t, 4H), 3.65 (t, 4H), 3.57 (s, 4H), 3.55 (s, 8H), 2.43 (s, 6H).
1,17-Bis(tosyloxy)-3,6,9,12,15-p en ta oxa h ep ta d eca n e [Ts-
(OCH2CH2)6OTs, 2(6)]. A clear, colorless oil19 was obtained in
(16) Ouchi, M.; Inoue, Y.; Kanzaki, T.; Hakushi, T. J . Org. Chem.
1984, 49, 1408-1412.
(17) Bartsch, R. A.; Liu, Y.; Kang, S. I.; Son, B.; Heo, G. S.; Hipes,
P. G.; Bills, L. J . J . Org. Chem. 1983, 48, 4864-4869.
(18) Fenton, D. E.; Parkin, D.; Newton, R. F. J . Chem. Soc., Perkin
Trans. 1 1981, 449-454.
(19) Newcomb, M.; Moore, S. S.; Cram, D. J . J . Am. Chem. Soc. 1977,
99, 6405-6410.

6872 J . Org. Chem., Vol. 64, No. 18, 1999
Notes
99% yield: 1H NMR (300 MHz, CDCl3) δ 7.78 (d, 4H), 7.32 (d,
4H), 4.12 (t, 4H), 3.65 (t, 4H), 3.58 (s, 4H), 3.55 (s, 12H), 2.43 (s,
6H).
mL THF was added dropwise, and the mixture was stirred for
96 h at room temperature. The solid was removed by filtration,
and the organic filtrate was washed with saturated aqueous
NaCl, dried over MgSO4, and concentrated to give a quantitative
yield of 4(7) as a yellow gellike liquid:15 1H NMR (300 MHz,
CDCl3) δ 7.45 (d, 12H), 7.18-7.30 (m, 18H), 3.59-3.69 (m, 24H),
3.19-3.25 (t, 4H).
1,1,1,21,21,21-Hexaph en yl-2,5,8,11,14,17,20-h eptaoxah en i-
cosa n e [Tr (OCH2CH2)6OTr , 4(6)]. A yellow, gellike liquid15
was prepared by reacting Tr(OCH2CH2)2OH with Ts(OCH2CH2)2-
OTs: 1H NMR (300 MHz, CDCl3) δ 7.45 (d, 12H), 7.18-7.28 (m,
18H), 3.62 (m, 20H), 3.20 (t, 4H).
1,1,1,27,27,27-H exa p h en yl-2,5,8,11,14,17,20,23,26-n on a -
oxa h ep ta cosa n e [Tr (OCH2CH2)8OTr , 4(8)]. A yellow gellike
liquid15 was prepared by reacting Tr(OCH2CH2)2OH with Ts-
(OCH2CH2)4OTs: 1H NMR (300 MHz, CDCl3) δ 7.48 (d, 12H),
7.18-7.23 (m, 18H), 3.60-3.78 (m, 28H), 3.20-3.30 (t, 4H).
1,1,1,30,30,30-Hexa p h en yl-2,5,8,11,14,17,20,23,26,29-d eca -
oxa tr icon ta n e [Tr (OCH2CH2)9OTr , 4(9)]. A yellow gellike
liquid was prepared by reacting Tr(OCH2CH2)3OH with Ts-
(OCH2CH2)3OTs: yield 98%; 1H NMR (300 MHz, CDCl3) δ 7.45
(d, 12H), 7.18-7.30 (m, 18H), 3.58-3.69 (m, 32H), 3.19-3.25
(t, 4H).
1,1,1,33,33,33-H exa p h en yl-2,5,8,11,14,17,20,23,26,29,32-
d od eca oxa tr itr ia con ta n e [Tr (OCH2CH2)10OTr , 4(10)]. A
yellow gellike liquid was prepared by reacting Tr(OCH2CH2)4-
OH with Ts(OCH2CH2)2OTs: yield 99%; 1H NMR (300 MHz,
CDCl3) δ 7.44 (d, 12H), 7.17-7.30 (m, 18H), 3.57-3.68 (m, 36H),
3.20 (t, 4H).
1,20-Bis(t osyloxy)-3,6,9,12,15,18-h exa oxa eicosa n e [Ts-
(OCH2CH2)7OTs, 2(7)]. A clear, colorless oil20 was obtained in
99% yield: 1H NMR (300 MHz, CDCl3) δ 7.78 (d, 4H), 7.32 (d,
4H), 4.12 (t, 4H), 3.65 (t, 4H), 3.56 (m, 20H), 2.43 (s, 6H).
1,23-Bis(tosyloxy)-3,6,9,12,15,18,21-h eptaoxatr icosan e [Ts-
(OCH2CH2)8OTs, 2(8)]. A clear, colorless oil15 was obtained in
99% yield: 1H NMR (300 MHz, CDCl3) δ 7.78 (d, 4H), 7.32 (d,
4H), 4.12 (t, 4H), 3.65 (t, 4H), 3.56 (m, 24H), 2.43 (s, 6H).
1,29-Bis(tosyloxy)-3,6,9,12,15,18,21,24,27-n on a oxa n on a -
cosa n e [Ts(OCH2CH2)10OTs, 2(10)]. A clear, colorless oil was
obtained in 99% yield: 1H NMR (300 MHz, CDCl3) δ 7.78 (d,
4H), 7.32 (d, 4H), 4.12 (t, 4H), 3.65 (t, 4H), 3.56 (m, 32H), 2.43
(s, 6H).
1,41-Bis(tosyloxy)-3,6,9,12,15,18,21,24,27,30,33,36,39-tr ide-
ca oxa h en tetr a con ta n e [Ts(OCH2CH2)14OTs, 2(14)]. Ditosy-
late 2(14) was prepared as described for tetraethylene glycol
ditosylate except that the reaction time was extended to 16 h.
After the reaction was finished, a mixture of 10/1 CH2Cl2 and
ice-water was added to the reaction mixture until the solids
dissolved. The organic layer was separated, and the aqueous
layer was extracted with CH2Cl2. The combined organic solutions
were washed with saturated NaCl solutions and dried over Na2-
SO4 overnight. Removal of Na2SO4 and solvent gave a clear,
colorless viscous oil in 97% yield: 1H NMR (300 MHz, CDCl3) δ
7.78 (d, 4H), 7.32 (d, 4H), 4.12 (t, 4H), 3.65 (t, 4H), 3.56 (m, 48H),
2.43 (s, 6H).
1,1,1,45,45,45-H exa p h en yl-2,5,8,11,14,17,20,23,26,29,32,-
35,38,41,44-p en ta tetr a con ta n e [Tr (OCH2CH2)14OTr , 4(14)]
was prepared by reacting Tr(OCH2CH2)4OH with Ts(OCH2CH2)6-
OTs. Removal of the MgSO4 and concentration of the solvent
gave a brownish-yellow solution. The solution was refluxed over
charcoal overnight and filtered to give a pale yellow solution.
Removal of the solvent gave a viscous pale yellow liquid in 97%
yield: 1H NMR (300 MHz, CDCl3) δ 7.44 (d, 12H), 7.17-7.30
(m, 18H), 3.57-3.68 (m, 52H), 3.20 (t, 4H).
Eth ylen e Glycol Oligom er Mon otr ityla tes a n d Ditr ity-
la t es. 7,7,7-Tr ip h en yl-2,5-d ioxa h ep t a n -1-ol [Tr (OCH2-
CH2)2OH, 3(2)]. A 500 mL three-neck round-bottom flask
equipped with a mechanical stirrer, thermometer, and nitrogen
inlet was charged with diethylene glycol (106 g, 1.00 mol) and
pyridine (11.9 g, 0.150 mol). With the mixture heated and
maintained at 45 °C, powdered trityl chloride (27.9 g, 0.100 mol)
was added to the reaction mixture under vigorous stirring. After
being stirred at 45 °C for 16 h, the suspension was filtered, and
the white solid was washed with distilled water. The crude
product was recrystallized once from 2-propanol and twice from
2/1 EtOAc/hexanes to give a white crystalline solid: yield 71%;
1H NMR (300 MHz, CDCl3) δ 7.46 (d, 6H), 7.25 (m, 9H), 3.58-
3.77 (m, 6H), 3.24 (t, 2H), 2.06 (t, 1H); mp 113.0-114.5 °C (lit.15
mp 112.7-114.5 °C).
10,10,10-Tr iph en yl-3,6,9-tr ioxadecan -1-ol [Tr (OCH2CH2)3-
OH, 3(3)]. 3(3) was prepared as described for diethylene glycol
monotritylate. After the reaction was finished, the reaction
mixture was poured into a separatory funnel, and an equal
volume of distilled water was added. The mixture was shaken
vigorously and allowed to settle for 2 h. The bottom layer was
separated from the aqueous solution, and the aqueous solution
was extracted with toluene. The product was dissolved in toluene
and combined with the toluene extract. The toluene solution was
washed with distilled water and dried over MgSO4 overnight.
Removal of the solid and solvent gave a yellow viscous gellike
liquid21 in 99% yield. The product was used for next reaction
without further purification: 1H NMR (300 MHz, CDCl3) δ 7.46
(d, 6H), 7.25 (m, 9H), 3.59-3.75 (m, 10H), 3.22 (t, 2H), 1.70 (s,
1H).
13,13,13-Tr ip h en yl-3,6,9,12-t et r a oxa t r id eca n -1-ol [Tr -
(OCH2CH2)4OH, 3(4)] was prepared and purified as described
for 3(4) to give a yellow viscous gellike liquid22 in 99% yield:
1H NMR (300 MHz, CDCl3) δ 7.46 (d, 6H), 7.20-7.45 (m, 9H),
3.25-3.15 (m, 12H), 3.12-3.08 (t, 2H), 3.26 (t, 2H), 2.35 (s, 1H).
Gen er a l P r oced u r e for th e P r ep a r a tion of Ditr ityla tes.
1,1,1,24,24,24-Hexa p h en yl-2,5,8,11,14,17,20,23-oct a oxa t et -
r a cosa n e [Tr (OCH2CH2)7OTr , 4(7)]. A 500 mL Schlenk flask
with an argon inlet was charged with NaH (3.00 g, 0.125 mol).
A solution of diethylene glycol monotritylate (34.8 g, 0.100 mol)
in 200 mL of THF was added dropwise, and the mixture was
stirred for 24 h. Ts(OCH2CH2)3OTs (23.0 g, 0.050 mol) in 150
Gen er a l P r oced u r e for th e Syn th esis of Exa ct Len gth
Eth ylen e Glycol Oligom er s. 3,6,9,12,15,18-Hexaoxaeicosan e-
1,20-d iol [H(OCH2CH2)7OH, 1(7)]. A high-pressure Monel
bomb with a glass insert was charged with 36.6 g (45.0 mmol)
of heptaethyelene glycol ditritylate, 150 mL of CH2Cl2, and 0.677
g of 10% palladium on carbon. Hydrogenolysis was carried out
at room temperature under 50 atm of H2 for 48 h. Upon
completion of the reaction, the catalyst (which can be reused)
was filtered and washed with CH2Cl2. The filtrate was concen-
trated to give a mixture of a white solid (triphenylmethane) and
an oil. The mixture was dissolved in boiling methanol, and the
majority of the triphenylmethane crystallized when the solution
was cooled to 0 °C. The mixture was filtered, and the filtrate
was washed with hexanes six times to remove trace amounts of
triphenylmethane. The solvent was removed to give a clear,
colorless oil: yield 97%; bp 180-195 °C/50 mTorr (lit.23 bp 200-
1
208 °C/300 mTorr); H NMR (300 MHz, CDCl3) δ 3.72-3.67 (t,
4H), 3.66-3.61 (m, 20H), 3.60-3.55 (t, 4H), 2.9 (s, 2H).
3,6,9,12,15-P en t a oxa h ep t a d eca n e-1,17-d iol [H (OCH 2-
CH2)6OH, 1(6)]: clear, colorless oil; yield 99%; 1H NMR (300
MHz, CDCl3) δ 3.72-3.67 (t, 4H), 3.66-3.61 (m, 16H), 3.60-
3.55 (t, 4H), 2.9 (s, 2H); bp 197-205 °C/100 mTorr (lit.24 bp 201-
205 °C/700 mTorr).
3,6,9,12,15,18,21-Hep ta oxa tr icosa n e-1,23-d iol [H(OCH2-
1
CH2)8OH, 1(8)]: clear, colorless oil;15 yield 97%; H NMR (300
MHz, CDCl3) δ 3.72-3.55 (m, 32H), 2.7 (s, 2H).
3,6,9,12,15,18,21,24-Oct a oxa h exa cosa n e-1,26-d iol
[H -
1
(OCH2CH2)9OH, 1(9)]: clear, colorless oil; yield 92%; H NMR
(300 MHz, CDCl3) δ 3.72-3.55 (m, 36H), 2.7 (s, 2H).
3,6,9,12,15,18,21,24,27-Non a oxa n on a cosa n e -1,29-d iol
[H(OCH2CH2)10OH, 1(10)]: clear light yellow oil; yield 96%; 1H
NMR (300 MHz, CDCl3) δ 3.72-3.56 (m, 40H), 2.58 (s, 2H).
3,6,9,12,15,18,21,24,27,30,33,36,39-Non a oxa h en tetr a con -
ta n e-1,41-d iol [H(OCH2CH2)14OH, 1(14)]: white waxy solid;
(20) Weber, E. J . Org. Chem. 1982, 47, 3478-3486.
(21) Huszthy, P.; Bradshaw, J . S.; Zhu, C. Y.; Izatt, R. M.; Lifson,
S. J . Org. Chem. 1991, 56, 3330-3336.
(22) Kaatsrichters, V. E. M.; Zwikker, J . W.; Keegstra, E. M. D.;
J enneskens, L. W. Synth. Commun. 1994, 24, 2399-2409.
(23) Warshawsky, A.; Kalir, R.; Deshe, A.; Berkovitz, H.; Patchornik,
A. J . Am. Chem. Soc. 1979, 101, 4249-4258.
(24) Newkome, G. R.; Nayak, A.; McClure, G. L.; Danesh-Khoshboo,
F.; Broussard-Simpson, J . J . Org. Chem. 1977, 42, 1500-1508.

Notes
J . Org. Chem., Vol. 64, No. 18, 1999 6873
yield 96%; 1H NMR (300 MHz, CDCl3) δ 3.72-3.56 (m, 56H),
2.58 (s, 2H); mp 37-39 °C.
NaCl solution, dried over MgSO4, and concentrated. The hexyl
and octyl derivatives for y ) 2-5 were distilled under vacuum
to give clear, colorless oils. All other compounds were recrystal-
lized from acetone (y ) 2, 3) or methanol (y ) 4-8, 10, 14) at
low temperature. Liquid products are clear and colorless, while
the solid products are white and crystalline.
P r ep a r a tion of ABA Am p h ip h iles [CH3(CH2)x-1(OCH2-
CH2)yO(CH2)x-1CH3, CxEOyCx]. Under Ar, the appropriate
ethylene glycol oligomer (5.00 mmol) in 20 mL of dry THF was
added dropwise to a 100 mL Schlenk flask charged with NaH
(12.5 mmol). The reaction mixture was stirred for 24 h, and then
the appropriate alkyl bromide (10.2 mmol) in 15 mL of THF was
added and stirred for 72 h at room temperature or at reflux (y
) 2, 3). Upon completion of the reaction, 5 mL of water was
added slowly, and the solution was stirred for 10 min. The layers
were separated, and the water layer was extracted with ether.
The combined organic solutions were washed with saturated
Su p p or tin g In for m a tion Ava ila ble: Physical data (1H
NMR), yields, and melting and boiling points for CxEOyCx (x
) 6, 8, 10, 12, 14, 16; y ) 2-8, 10, 14). This material is
available free of charge via the Internet at http://pubs.acs.org.
J O990620M