tract was dried over sodium sulfate and evaporated to dryness. The residue was dissolved in hot «-butyl ether. Upon cooling 0.36 g. of dihydrodeguelic acid separated which had the properties recorded for the acid obtained by catalytically reducing deguelic acid. Summary 1.Derric and risic acids have been obtained from deguelic acid by methods analogous to those used in preparing these acids from derivatives of rotenone. This shows that in deguelin as in rotenone, derric acid constitutes one-half of the molecule.2. Reduction of dehydrodeguelin yields dihydrodehydrodeguelin, which is identical with dehydro-j3-dihydrorotenone.3. Upon treatment with alcoholic alkali, dihydrodehydrodeguelin gives dihydrodeguelic acid. This acid is also obtained by catalytically reducing deguelic acid.4. Dihydrodeguelic acid has been found to be identical with dehydrodihydroxy-0-dihydrorotenonic acid described by Haller.5. These facts show that there exist structural relationships common to the entire molecule of both rotenone and deguelin.

In establishing the fact that properly substituted diphenylbenzenes with two points of restricted rotation gave rise to two diastereoisomeric forms, the cis and trans (I) forms of 3,6-di-(2,5-dimethylphenyl) -2,5-dibromohydr~quinone~ and the cis and trans (11) forms of 3,6-di-(3-bromo-2,4,6 -trirnethylphenyl) -2,5 -dibromohydroquinone3 were synthesized. The former pair (I) yielded the same quinone on oxidation which, in turn, on reduction resulted in a mixture of the original hydroquinones. Each of the latter pair (11), however, gave a well-defined individual series of compounds ; especially may be mentioned the corresponding quinone (111) and from this the tetrahydroxybenzene (IV) as illustrated by the trans modification (11). CHsBr OH /--\ I less-soluble a-form (11) resulted in failure. The dimenthoxyacetates of each form were synthesized from the hydroquinone and menthoxyacetyl chloride. From the @-form (V) two diastereoisomeric esters (VI) were produced which could be separated by crystallization from acetone. By hydrolysis of these two products the two active forms of the hydroquinone (V) were obtained. By oxidation of the active forms the corresponding active quinones were synthesized which had opposite signs of rotation from the hydroquinones. These quinones were readily re. duced to the original active hydroquinones.The a-or trans form (11) gave a dimenthoxyacetate which existed in two crystalline modifications, one m. p. 146-147' and one m. p. 167-At the time of these investigations just mentioned it was assumed that the higher-melting, less-soluble isomers were trans modifications, which from a stereochemical standpoint would be meso, and they were designated as a-forms. The lower-melting, more-soluble isomers were assumed to be cis or racemic and were called 8-forms. Many attempts to confirm experimentally the individual cis and trans forms by resolution of the racemic modification resulted in failure owing to the difficulty of introducing satisfactory salt-forming groups.Resolution of the more soluble &form (V) of 3,6 -di -(3 -bromo -2,4,6 -trimethylphenyl) -2,-5-dibromohydroquinone has now been accomplished, while a similar attempt to resolve the (1) Por the lart yaper i n this series see Chang and Adams, THIS IOWRNAL, 56, 2080 (1034): also Adams and Yiian, f h r m . Rrr;.. 12, 281 (1933). ( 2 ) Browning and Adams, ibid., 62,4098 (1930). (3) Shildneck and Adams, ibid., 63, 343, 2203 (1931). 168'. They were observed during the crystallization from either alcohol or acetone, when two types of crystals separated, small round opaque Br CH, Br OH CH, Br CHI CH3 V CH?OCioHjg co I I co ICHsOCioHi 9 VI. Two diastereoisomers clusters of tiny crystals and large transparent crystal clusters. The former were the low-melting form, the latter the high-melting form. If

No abstract

S‐methyl isothiourea sulfate S‐methyl isothiourea sulfate

The gas produced was analyzed in an Orsat-Williams apparatus, being collected over water previously saturated with the gas. The saturated hydrocarbon was calculated as methane. SummaryThe decomposition of acetic acid in the presence of silica gel at a temperature range of 400-500°has been studied.Silica gel is an effective catalyst for the conversion of acetic acid to acetone. At least 85% of the acetic acid decomposed in the presence of silica gel produces acetone.