Methyl, alcohol Rearrangement

To obtain a maximum yield of the acid it is necessary to hydrolyse the by-product, iaoamyl iaovalerate this is most economically effected with methyl alcoholic sodium hydroxide. Place a mixture of 20 g. of sodium hydroxide pellets, 25 ml. of water and 225 ml. of methyl alcohol in a 500 ml. round-bottomed flask fitted with a reflux (double surface) condenser, warm until the sodium hydroxide dissolves, add the ester layer and reflux the mixture for a period of 15 minutes. Rearrange the flask for distillation (Fig. II, 13, 3) and distil off the methyl alcohol until the residue becomes pasty. Then add about 200 ml. of water and continue the distfllation until the temperature reaches 98-100°. Pour the residue in the flask, consisting of an aqueous solution of sodium iaovalerate, into a 600 ml. beaker and add sufficient water to dissolve any solid which separates. Add slowly, with stirring, a solution of 15 ml. of concentrated sulphuric acid in 50 ml. of water, and extract the hberated acid with 25 ml. of carbon tetrachloride. Combine this extract with extract (A), dry with a httle anhydrous magnesium or calcium sulphate, and distil off the carbon tetrachloride (Fig. II, 13, 4 150 ml. distiUing or Claisen flask), and then distil the residue. Collect the wovaleric acid 172-176°. The yield is 56 g. 

The reaction proceeds via a pentacoordinate hydroxycarbonium ion transition state, which cleaves to either fert-butyl alcohol or the tert-butyl cation. Since 1 mol of isobutane requires 2 mol of hydrogen peroxide to complete the reaction, one can conclude that the intermediate alcohol or carbocation reacts with excess hydrogen peroxide, giving fcrt-butyl hydroperoxide. The superacid-induced rearrangement and cleavage of the hydroperoxide results in very rapid formation of the dimethylmethyl-carboxonium ion, which, upon hydrolysis, gives acetone and methyl alcohol. 

Orthanilic acid was first made by the reduction of nitro-benzenesulfonic acid by ammonium sulfide.2 This reduction has also been carried out electrolyticallv, and by the use of iron or zinc.3 The acid has also been made by the rearrangement of phenylsulfamic acid,4 by the action of sodium hypobromite upon potassium o-carbaminebenzenesulfonate,5 by the reduction of the mixed nitrobenzenesulfonic acids followed by separation of the isomers,6 by the action of methyl alcohol upon o-nitro-phenylsulfurchloride,7 by the action of acid upon diacetyl diphenylsulfamide,8 by the debromination of />-bromoaniline-e-sulfonic acid,9 by the reduction of 1,2,6-aminothiophenolsulfonic acid,10 and by the hydrolysis and reduction of e-nitrobenzene-sulfonyl chloride, which was obtained from di-o-nitrophenyl-disulfide.11... 

Although the ethyl urethans have been the ones most commonly prepared from azides, almost any urethan can be prepared with the appropriate alcohol. Rearrangement in methanol usually succeeds as well as in ethanol, but occasionally, because the decomposition temperature of the azide may be above the boiling point of methanol, the azide is recovered unchanged or is converted to the methyl ester. ... 

Additional evidence for carbocation intermediates in certain nucleophilic substitutions comes from observing rearrangements of the kind normally associated with such species For example hydrolysis of the secondary alkyl bromide 2 bromo 3 methylbutane yields the rearranged tertiary alcohol 2 methyl 2 butanol as the only substitution product... 

FREUDENBERG - SCHdNBERG Xanthate Rearrangement Rearrangement of S-methyl xanthates to S-methyIdithiocarbonatas (conversion of alcohols lo thiols via xanthates, also phenols to thiophenols via thiocarbamates). 

This method of preparation is suitable for producing primary alkyl lactates but is unsatisfactory for /3-methallyl lactate because the strong mineral acid catalyzes the rearrangement of methallyl alcohol to isobutyraldehyde. Methyl lactate can be made conveniently (80-85% yield) by heating 1 mole of lactic acid condensation polymer with 2.5-5 moles of methanol and a small quantity of sulfuric acid at 100 for 1-4 hours in a heavy-walled bottle, such as is used for catalytic hydrogenation with a platinum catalyst. 

The preparation of neopentyl alcohol from diisobutylene herein described represents an example of acid-catalyzed addition of hydrogen peroxide to a branched olefin, followed by an acid-catalyzed rearrangement of the tertiary hydroperoxide formed. In addition to neopentyl alcohol, there are formed acetone and also small amounts of methanol and methyl neopentyl ketone by an alternative rearrangement of the hydroperoxide. 

---