acid obtained by heading the an hydride of the trans-acid, forms prisms which melt at 192° C. .When heated with hydrochloric acid it passes into the trans-variety. The racemic trans-acid is produced by the reduction of the dihydrobromide of A*-tetrahydrophthalic acid or AM dihydrophthalic acid. It is split into its active components by means of its quinine salt (A. Werner and H. E. Conrad, Bef., 1899, 32, p. 3046). Hexahydroisophthalic acids (cyclo-hexane-1~3dicarboxylic acids) are obtained by the action of methylene iodide on disodio-pentane tetracarboxylic ester (W. H. Perkin, Joum. Chem. Soc., 1891, 59, p. 798); by the action of trim ethylene bromide on disodio-propane tetracarboxylic ester; and by the reduction of isophthalic acid with sodium amalgam, the tetrah dro acids first formed being converted into hydro bromides and fiiirther reduced (A. v. Baeyer and V. Villiger, Ann., 1893, 276, p. 255). The cisand trans- forms can be separated by means of their sodium salts. The trans-acid is a racemic compound, which on heating with acetyl chloride gives the an hydride of the-cis-acid.-Hexahydroterephthalic acids (cyclo-hexane~1-4-dicarboxylic acids). These acids are obtained by the reduction of the hydro bromides of the di- and tetra-hydroterephthalic acids or by the action of ethylene dibromide on disodio-butane tetracarboxylic acid. An important derivative is succino-succinic acid, C61-l6O2(CO¢H)2, or cyclo-hexanedione-2-5-dicarboxylic acid-1-4, which is obtained as its ester gyhtihe action of sodium or sodium Iethylate on succinic ester (H. e ing, mi., 1844, 49, p. 192; .
Hermann, Ann., 1882, 211, p. 306). 5”d'“"“"" It crystallizes in needles or prisms, and dissolves in alcohol to form a bright
blue fluorescent liquid, which on the
with acetic an hydride. When boiled, with caustic soda it isomerizes to a mixture of the AM and AM dihydrophthalic acids. The A24 acid is obtained by boiling the dihydrobromide of the AM acidwith alcoholic potash or by continued boiling of the AM acid with caustic soda.
The AM acid is formed when phthalic acid is reduced in the cold by sodium amalgam or by heating the AM and AM acids with caustic soda. The trans-modification of A3'5 acid is produced when phthalic acid is reduced by sodium amalgam in the presence of acetic acid. When heated for some time with acetic an hydride it changes to the cis-form. The trans-acid has been resolved by means of its strychnine salts into two optically active isomer ides, both of which readily pass to AM dihydrophthalic acid (A. Neville, Journ. Chem. Soc-. 1906. 89. P- 1744)- .
Of the dihydroterephthalic acids, the Am acid is obtained by heat ing the dibromide of theA' tetra hydro acid with alcoholic potash. It cannot be prepared by a direct reduction of terephthalic acid. On warming with caustic soda it is converted into the AN acid. TheA"“ acid is also obtained by the direct reduction of terephthalic acid. It is the most stable of the dihydro acids. The A” acid is obtained by boiling the cis- and trans-AM acids with water, which are obtained on reducing terephthalic acid with sodi um amalgam in faintly alkaline solution. The relationships existing between the various hydrophthalic acids may be shown as follows:- algam (hat) Sodium amalgam + acetic acid PHTHALIC Acm-Sodium
A3'5 Dmvmzo (TRANS.) A
addition of ferric chloride becomes A2 and A4 TETRAHYDR0 Sodium A 2-5 Dgypao Alkali J/ Acetic' an hydride cherry red. The acid on heating loses ~ J/Heat #"m1l§ Gm(h0t) A3'5 DmyDp 0(¢15) CO2 and gives cyclo-hexanedione-1-4. MT H3'f";1b7Z""'1ia'”;"h, Tetrahydrobenzaic acid (cyclo-hexene- ETRAHY“° V am 0" P" S 1-carboxylic acid-1), CGH9-COgH. Three AN Drnvmio structural isomers are possible. The Hydfvbfvmifk A1 acid results on boiling the A' acid
with alkalis, or on eliminating hydro bro mic acid from 1-brom-cyclo-hexanecarboxylic acid-1. The A' acid is
formed on the reduction of benzoic acid with sodium amalgam. The A3 acid is
obtained by eliminating the elements of water from 4-oxy-cyclo-hexane-1-carboxylic acid (W. H. Perkin, °un., Journ.
Chem. Soc., 1904, 85, p. 431) Shikimic
acid (3-4-6-trioxy-A1-tetrahydrobenzoic acid) is found in the fruit of Illicium feligiosum. On fusion with alkalis it
yields para-oxybenzoic acid, and nascent hydrogen reduces it to hydroshikimic
acid. Sedanolic acid, CHHNO3,
which is found along withlsedanonic
acid, C12H1@()3, in the higher boiling
fractions of celery oil, is an ortho-A
acetic an hydride
A 1'4 DLHYDRO
Sodium amalgam in
Sogfum faintly alkaline solution
“'" g“"' V sodium
Bail wah A2'5 Drmmizo amalgam
L Boil with water (hot)
wat" A 1'5 Dmvrmo
/'Sodium amalgam Bo”+ NaOH
3 A2 Tmmuvnno A 1 Tnrulnvnno
Dibmmide + H ydrobromida
Reduce alcoholic potash an reduction
/ Remove H Br from
A 1'3 DIHYDRO, Hrxmnnno
oxyamyl-A5-tetrahydrobenzoic acid, sedanonic acid being orthovaleryl-A1-tetrahydrobenzoic acid (G. Ciamician and P. Silber, Bef., 1897, 30, pp. 492, 501, 1419 seq.). Sedanolic acid readily decomposes into water and its lactone sedanolid, C1¢H1gO2, the odorous constituent of celery oil.
Tetrahydrophthalic acids (cyclo - hexene dicarboxylic acids), C5H., (CO1H)2. Of the ortho-series four acids are known. The A* acid is obtained as its an hydride by heating the A2 acid to 220° C., or by distilling hydropyromellitic acid. Alkaline potassium permanganate oxidizes it to adipic acid. The A” acid is formed along with the A4 acid by reducing phthalic acid with sodium amalgam in hot solutions. The A* acid exists in cis- and transforms. The trans-variety is produced by reducing phthalic acid, and the cis-acid by reducing A24 dihydrophthalic acid. In the meta-series, four acids are also known. The A2 acid is formed along with the A4 (cis) acid by reducing isophthalic acid. The trans A4 acid is formed by heating the cis-acid with hydrochloric acid under pressure. The A' acid is formed when the an hydride of tetra hydro rimesic acid is distilled (W. H. Perkin, junr., Journ. Chem. Soc., 1905, 87, p. 293).-In
the para-series, three acids are known. The A1 acid is formed by the direct reduction of terephthalic acid; by boiling the A” acid with caustic soda; and by the reduction (in the heat) of Ai* dihydroterephthalic acid. The A' acid exists in cis- and trans- forms; these are produced simultaneously in the reduction of A" or AW dihydroterephthalic acids by sodium amalgam.
There are five possible dihydrobenzoic acids. One was obtained in the form of its amide by the reduction of benzamide in alkaline solution with sodium amal am (A. Hutchinson, Ber., 1891, 24, p. 177). The A" acid is oihtained on oxidizing dihydrobenzaldehyde with silver oxide or by the reduction of meta-trimethylaminobenzoic acid (R. Willstatter, Ber., 1904, 37, p. 1859). Cyclo-heptane (suberane), C1Hi4, obtained by the reduction of suberyl iodide, is a liquid which boils at 117° C. On treatment with bromine in the presence of aluminium bromide it gives chiefl pentabromtoluene. When heated with hydriodic acid to 230° it gives rnethylhexamethylene. On oxidation with nitric acid (sp. r. 1°4) it yields pimelic acid. Disuberyl, C, H13-C, H,3, a thick oily hquid, boiling at 290-291° C., is obtained by the reduction of suberyl bromide.
Cyclo-heptene, C7H12, is obtained by the action of alcoholic potash on suberyl iodide; and from cyclo-heptane carboxylic acid, 'the amide of which by the action of sodium hypo bro mite is converted into cyclo-hep tan amine, which, in its turn, is destructively methylated (R. Willstatter, Ber., 1901, 34, 131). Cyclo-heptadiene I-3, C7Hm, is obtained from cyclo-heptene (Willstatter, loc. cit.). It is identical with the hydrotropilidihe, which results by the destructive methylation of tropane.-Euterpeiie
(trim ethyl-1 -4-4-cyclo-heptadiene I -5), CWHM, is prepared from dihydroeucarveol. By the action of hydro bro mic acid (in glacial acetic acid solution) and reduction of the resulting product it yields 1-2-dimethyl-4-ethyl benzene (A. v. Baeyer, Bei., 1897, 0, p. 2075). Cyclo-heptatriene (tropilidine), C7Hg, , is formed on (Tistilling tropine with baryta; and from cyclo-heptadiene by forming its addition product with bromine and heating this with quinoline to ISO-160° C. (R. Willstiitter, loc. cit.). Chromic acid oxidizes it to benzoic acid and benzaldehyde. With bromine it forms a dibromide, which then heated to 110° C. decomposes into hydro bro mic acid and benz l bromide. 4
Cyclo-heptariol, C, Pi;3OH, is formed by the reduction of suberone, and by the action of silver nitrite on the hydrochloride of cyclohexanamine (N. Demjanow, Ceiitralblatt, 1904, i. p. 1214). Cyclo-hep tan one (suberone), C7H12O, is formed on the distillation of suberic acid with lime and from
Of the dihydrophthalic acids, five are known in the ortho-series, carboxylic acid by treatment with baryta and two of which are stereo-isomers of the cis- and trans-type, and a similar number are known in the para-series. The Al" acid is obtained as its an hydride by heating A" dihydrophthalic an hydride tion over lead peroxide (R. Willstatter, Bef.. It is a colourless liquid having a peppermint at 178-5-170-5° C. Nitric acid oxidizes it -brom-cyclo-heptane
31, D. 25Q7)odour,
to n-pimelic acid.