Boeseken, J.; Slooff, G.; Hoeffelman, J. M.; Hirsch, H. E. published the artcile< Action of 2-hydroxycyclopentanecarboxylic acids on the electrical conductivity of boric acid. Mobility of the cyclopentane ring>, Recommanded Product: (9Z,12Z)-Methyl octadeca-9,12-dienoate, the main research area is .
Aliphatic α-OH acids exert a very pronounced action on the elec. conductivity of H3BO3, while β-OH acids are indifferent. Although aromatic o-hydroxy carboxylic acids are β-OH acids, they exert a pos. action on the conducting power of H3BO3 comparable with that of aliphatic α-OH acids. Evidently the position of the OH and CO2H groups is very favorable to “”aromatic tension””-the tension due to the fact that all the groups united directly with the benzene ring are forced to lie in the plane of the ring. It was to be expected that the cis-2-hydroxycyclopentanecarboxylic acids, being β-OH acids, could exert a pos. action on the conductivity of H3BO3, not only because the complex activities of the open chain β-OH acids have disappeared, but also because the position of the OH and CO2H groups in the cis-isomers is favorable to the formation of a hexatomic ring. Results obtained by the authors in the investigation of certain acids have confirmed this hypothesis. Two 2-borneol-3-carboxylic acids are known, I (m. 102°) and II (m. 175°). I increases the conductivity of H3BO3 and is therefore the cis-isomer; this is also in accord with the values of the electrolytic dissociation constant The fact that II is difficultly attacked by KMnO4 is proof of its trans-configuration, for in the trans-isomer the OH and CO2H groups are not situated in such a way as to favor the formation of a complex with KMnO4. II does not react with Me2CO or chloral; I reacts with Me2CO to give a solid, m. 124°, and with chloral to give a chloralide, m. 191°. 2-Hydroxycyclohexanecarboxylic acid (III), only 1 form (m. 111°) of which the authors were able to obtain, decreased the conductivity of H3BO3. The cyclohexane ring being much more mobile than the pentatomic ring, the OH and CO2H groups will occupy a much less fixed position in this acid than in the hydroxycyclopentanoic acids. In that case the situation in the cis-isomer may be almost as unfavorable as in the trans-isomer. Although a chloralide (m. 142°) of III was obtained, this is no more a proof that the acid has the cis-configuration than the neg. conduction with reference to H3BO2 is a proof of the trans-configuration. From the mother liquors of some preparations of III was obtained a small quantity of a sirup. After distillation it crystallized slowly to a solid which m. 57-63° and increased the conductivity of H3BO3. At best it may be said that III is probably the trans-acid. Cyclization of Et adipate by Na, reduction of the product with H2 and Ni, treatment with KOH in MeOH and addition of acid gave a viscous oil which would not crystallize. This mixture of cis- and trans-2-hydroxycyclopentanecarboxylic acids was separated by means of Me2CO, since only the cis-isomer forms a volatile cyclic acetal with Me2CO. During acetonization in the presence of P2O5 the trans-acid was transformed into its cis-isomer. The Me2CO compounds when hydrolyzed gave acids which increased the conductivity of H3BO3, indicating their cis-configuration. To Et 3-methyladipate in PhMe was added a few drops of absolute EtOH and some Na wire. After the vigorous reaction had ceased, the solid mass of Na salts was heated for a time at 150°, then suspended in Et2O and acidified. The product b40 130-5° and on reduction with H2 and Ni at 150-60° under pressure gave a mixture of the esters of 4- and 5-methyl-2-hydroxycyclopentanecarboxylic acids, b. 72-82° in cathode vacuum. Saponification of the esters gave a mixture of cis- and trans-acids, which was separated by acetonization in the presence of P2O5. No isomerization of trans-acid to the cis-acid occurred, owing to stabilization by the Me group of the cyclopentane ring. From the Me2CO solution was obtained on distillation the Et ester of 5-methyl-2-hydroxycyclopentanecarboxylic acid, b2 115-7°. The marked difference between the increase in conductivity of H3BO3 (0.5 M) produced by borneolcarboxylic acid and that produced by the simple cyclopentanolcarboxylic acids is attributed by the authors to a much more pronounced rigidity of the pentatomic rings of borneol.
Recueil des Travaux Chimiques des Pays-Bas et de la Belgique published new progress about Acids. 112-63-0 belongs to class esters-buliding-blocks, and the molecular formula is C19H34O2, Recommanded Product: (9Z,12Z)-Methyl octadeca-9,12-dienoate.
Referemce:
Ester – Wikipedia,
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