Organic Syntheses, Coll. Vol. 7, p.397 (1990); Vol. 60, p.11 (1981).
CARBOXYLIC ACIDS FROM THE OXIDATION OF TERMINAL ALKENES BY PERMANGANATE: NONADECANOIC ACID
A 5-L, three-necked, round-bottomed flask fitted with a mechanical stirrer
is placed in an ice bath
and charged with 1000 mL of distilled water, 120 mL of 9 M sulfuric acid, 3.0 g of Adogen 464 (Note 1)
, 20 mL of glacial acetic acid, 1000 mL of methylene chloride
, and 50 g of 1-eicosene (Note 2)
. The solution is rapidly stirred and 80 g (0.544 mol) of potassium permanganate
is added in small portions over a 3-hr period (Note 3)
. Stirring is continued for an additional 18 hr at room temperature. The mixture is cooled in an ice bath, and 60 g of sodium bisulfite
is added in small portions to reduce any precipitated manganese dioxide
. The solution is acidified, if basic, with sulfuric acid
and separated. The aqueous layer is extracted with two 400-mL portions of methylene chloride
. The organic extracts are combined, washed with two 400-mL portions of water, washed once with brine
, and concentrated to 400 mL on a rotary evaporator
. The resulting mixture is heated to dissolve any precipitated product, a small amount of amorphous solid is removed by filtration, and the filtrate is cooled to 0°C. A first crop of white crystals (33–36 g
, mp 67–68°C
) is collected by suction filtration and washed with a minimum amount of ice-cold methylene chloride
. Concentration of the mother liquor to 150 mL and cooling to 0°C yields a second crop of crystals (7–12 g
). The combined products are dissolved, with heating, in 400 mL of methylene chloride
and the pale-yellow solution is allowed to cool to room temperature, then slowly
to −10°C. The white crystals (36–37 g
) are collected, washed with a small amount of cold methylene chloride
, and dried in vacuum overnight (mp 68–68.5°C
67–68°C). The yield is 75–77% (Note 4)
Adogen 464, a methyl trialkylammonium (C8-C10) chloride, was obtained from Ashland Chemical Co.
Technical 1-eicosene was obtained from the Aldrich Chemical Company, Inc.
and used without further purification. Analysis by quantitative catalytic hydrogenation over Pd-C and NMR spectroscopy indicated that it contained about 10% unreactive, saturated hydrocarbon material.
The yield was calculated by assuming that the starting material contained 90% 1-eicosene
(see (Note 2)
is the preferred reagent for the oxidative cleavage of carbon-carbon double bonds.3
Because of its low solubility in nonpolar solvents, however, the reactions have traditionally been carried out in polar organic solvent systems. For example, the use of aqueous tert-butyl alcohol4
and acetic anhydride5
for this purpose has been described. An alternative approach involves the use of phase-transfer agents to solubilize permanganate ion in organic solvents and several examples of this approach have been reported.6
has often been used as the solvent,2
it has been observed that methylene chloride
is a superior solvent7
; better yields are obtained and because of its greater volatility it is more easily removed at the conclusion of the reaction. In addition, methylene chloride
is more resistant to oxidation by solubilized permanganate. Adogen 464
was used as the phase-transfer agent because the yields compared well with those obtained when other agents8
were used and because it is both inexpensive and readily available. The solutions were maintained acidic to neutralize hydroxide ions formed during the reduction of permanganate (MnO4−
O ρ MnO2
). In the absence of acetic acid
the accumulation of base promotes certain side reactions and increases the stickiness of the manganese(IV) oxides
which precipitate as the reaction proceeds.
The results obtained with a number of other representative terminal alkenes have been summarized in Table I.
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