67.8, 74.8. Anal. Calcd for C8H18O2: C, 65.7; H, 12.4. Found:
C, 65.3; H, 12.0.
collected and represented >95% pure 5-ethyl-3-methyleneno-
nane. Yield: 34 g, 14% (combined yield of 2-ethyl-1-hexene and
5-ethyl-3-methylenenonane: 83%) H NMR (CDCl3) δ 4.76 (s,
1H), 4.70 (s, 1H), 2.12–1.93 (m, 4H), 1.38–1.19 (m, 8H), 1.04
(t, 3H, J = 7.4 Hz), 0.98–0.81 (m, 6H). 13C NMR (CDCl3) δ:
150.7, 109.1, 41.3, 36.9, 32.8, 29.1, 28.6, 25.9, 23.3, 14.3, 12.5,
10.9. Anal. Calcd for C12H24: C, 85.63; H, 14.37. Found: C,
85.33; H, 14.55.
1
Method 2: Peracetic acid solution (15 mL, 71 mmol) was
added to a mixture of 2-ethyl-1-hexene (7.3 g, 65 mmol) and
15 mL of H2O. The mixture was heated at 50 °C for 2 h and
then 65 °C for an additional 2 h. After cooling to room tempera-
ture the mixture was extracted with ether and washed several
times with water. The organic layer was then dried over MgSO4
and the ether removed to yield a colorless oil (7.5 g, 81% yield
based on the GC distribution of diol and dioxolanes).
Oxidation of 5-ethyl-3-methylenenonane
Method 1: 5-ethyl-3-methylenenonane (7.5 g, 45 mmol) was
added to a peracetic acid solution (15 mL, 71 mmol) diluted in
15 mL of acetic acid. The mixture was heated to 50 °C for 2 h
and 65 °C for an additional 2 h. After cooling to room tempera-
ture, the mixture was extracted with ether and washed with
excess H2O to yield a total of 8.4 g of colorless oil. The product
was a complex mixture of diacetates, monoacetates, diols, and
epoxides. Under similar conditions, 5-ethyl-3-methylenenonane
(1.5 g, 8.9 mmol), peracetic acid solution (2.0 mL, 9.5 mmol)
and 5 mL H2O gave 1.6 g of product with a similar distribution.
Treatment of the crude mixtures with K2CO3 in methanol at
50 °C did not change the product distribution significantly.
Dehydration of 2-ethylhexan-1,2-diol (Nafion)
2-Ethyl-1,2-hexanediol (2.20 g, 15 mmol) and Nafion SAC-13
(1.00 g) were heated to 175 °C for 6 h. The flask was equipped
with a short path distillation column and a receiving flask, but no
significant distillate was observed over the course of the reaction.
The reaction mixture was decanted from the catalyst and ana-
lyzed by GC. A 20% conversion of the diol to a mixture of four
diastereomeric dioxolanes was observed.
Dehydration of 2-ethylhexan-1,2-diol (MMT-K10)
2-Ethyl-1,2-hexanediol (5.01 g, 34.3 mmol) was stirred with
MMT-K10 (1.8 g) in 50 mL of benzene at an oil bath tempera-
ture of 95 °C. The water generated in the reaction was collected
using a Dean-Stark trap. After 6 h the mixture was cooled to
room temperature and the MMT-K10 was removed by filtration.
Removal of the benzene under reduced pressure yielded 3.74 g
of a tan oil (85%). By GC-MS this procedure gave >95% con-
version to a mixture of four diastereomeric dioxolanes. The
NMR spectra were extremely complex due to the overlap of
peaks arising from the four isomers.
2-Ethyl-2-(2-ethylhexyl)oxirane/2,4-diethyloctane-1,2-diol
Method 2: In an adaptation of a published procedure,15 5-ethyl-
3-methylenenonane (1.4 g, 8.3 mmol) was dispersed in de-
ionized water (50 mL), the flask was cooled to 0 °C, and pow-
dered m-chloroperoxybenzoic acid (2.04 g (77%), 9.1 mmol)
was added in small portions over 5 min. The mixture was stirred
for 8 h at room temperature and then 1.5 mL of H2SO4 (10%)
was added and the flask left to stand for an additional 8 h. Solid
NaOH was then added until all solids dissolved. The aqueous
solution was saturated with NaCl and extracted with three 15 mL
aliquots of ethyl acetate. The extracts were dried with MgSO4
and the solvent removed under reduced pressure to give a color-
less oil (yield: 1.25 g, 80%). The mixture consisted of diastereo-
mers of 2-ethyl-2-(2-ethylhexyl)oxirane and 2,4-diethyloctane-
2-Ethylhexanal
A distillation apparatus was assembled consisting of a reaction
flask connected by a short curved glass tube to a Schlenk type
receiver. H2SO4 (2 mL, 9 M) was added to the reaction flask,
followed by 2-ethyl-1,2-hexanediol (0.91 g, 6.2 mmol). The
mixture was stirred at room temperature for 5 min and the reac-
tion flask then placed in a 100 °C oil bath. The pressure in the
apparatus was reduced by slowly opening the Schlenk flask to a
high vacuum line until vigorous boiling of the reaction mixture
was evident. The receiver flask was cooled in dry ice and the
products distilled until the reaction mixture turned dark red-
black. The system was periodically exposed to the vacuum line
to maintain rapid boiling. The resulting distillate was extracted
with ether, washed with aqueous NaHCO3 and water and dried
over MgSO4. Removal of the ether under reduced pressure
1
1,2-diol in a 4 : 1 ratio. H NMR of the diastereomeric oxiranes:
(CDCl3) δ: 2.59 (dd, 1H, J = 4.9, 0.8 Hz), 2.52 (dd, 1H, J = 4.9,
2.1 Hz), 1.70–1.49 (m, 3H), 1.45–1.15 (m, 11H), 0.94 (s, 1H,
–OH), 0.91 (s, 1H, –OH), 0.92–0.79 (m, 8H). 13C NMR
(CDCl3) δ: 59.57, 59.54, 52.85, 52.81, 38.2 (broad, overlap of
two peaks), 35.8 (broad, overlap of two peaks), 33.3, 33.0, 28.9,
28.8, 26.9 (broad, overlap of two peaks), 26.5, 26.1, 23.17,
23.15, 14.22, 14.20, 10.79, 10.73, 8.94, 8.91.
2,4-Diethyloctanal
1
yielded 0.72 g (90%) of 2-ethylhexanal (confirmed by H NMR
In a manner similar to that used for the synthesis of 2-ethyl-
hexanal, 2,4-diethyloctanal was prepared from the mixture of
2-ethyl-2-(2-ethylhexyl)oxirane and 2,4-diethyloctane-1,2-diol
spectroscopy).
1
(yield: 61%). H NMR (CDCl3) δ: 9.55 (s, 1H, HCvO), 9.53
5-Ethyl-3-methylenenonane
(s, 1H, HCvO), 2.32–2.19 (m, 1H), 1.77–1.42 (m, 3H),
1.42–1.13 (m, 10H), 1.03–0.79 (m, 9H). 13C NMR (CDCl3)
δ: 183.32 (broad, overlap of two peaks, HCvO), 45.15, 45.10,
37.0, 36.8, 36.05, 36.02, 33.0, 32.5, 28.7, 28.6, 26.1, 26.0, 25.9,
The pot residue from the synthesis of 2-ethyl-1-hexene was frac-
tionally distilled under nitrogen using a 9-inch vacuum jacketed
Vigreux column. Product distilling between 185 and 200 °C was
2452 | Green Chem., 2012, 14, 2450–2456
This journal is © The Royal Society of Chemistry 2012