Art. XLIII.—Studies on the Chemistry of the New Zealand Flora.

Transactions and Proceedings of the Royal Society of New Zealand, Volume 36, 1903, Page 483

Art. XLIII.—Studies on the Chemistry of the New Zealand Flora. By Thomas H. Easterfield, Professor of Chemistry in the Victoria College, and B. C. Aston, Chemist to the Department of Agriculture. [Read before the Wellington Philosophical Society, 2nd September, 1903.] Part III.—Rimu-resin. The wide distribution of resinous substances in the vegetable kingdom naturally raises three questions: (1.) What is the function of resins in the plant-economy? (2.) What is the chemical origin of the resins? (3.) Are all the plant-resins closely related from the chemical standpoint? it is in the hope of finding evidence which may help in arriving at an

answer to these questions that the present investigation been commenced. The rimu (Dacridium cupressinum) is one of the best known and most widely used of the New Zealand forest-trees; its timber is highly resinous, and the heart-shakes, which are frequently large, contain an opaque pinkish resin which may completely fill the cracks or only occur in warty globules having a concentric structure. Rimu-resin dissolves for the most part in alcohol, but leaves a small residue of a red amorphous substance, which has a bitter and astringent taste. If water be added to the alcoholic solution until a faint turbidity results, and the solution be allowed to stand for some hours, the greater part of the resin separates in the form of almost colourless hexagonal plates, which can be completely decolourised by recrystallisation from dilute alcohol. The crystalline compound thus obtained is strongly acid, and the name “rimuic acid” is proposed for it. Rimuic acid is very sparingly soluble in water, benzene, and light petroleum; easily soluble in alcohol, ether, and hot acetic acid. It melts at 192°–193°C., and has the specific rotation [a]d = − 150°. Two preparations of the acid were analysed. The analyses and molecular-weight determinations agree with the formula. C16H20O3. Calculated for Found. C16H20O3. I. II. c = 73.8 73.8 73.7 H = 7.7 7.9 7.95 O = 18.5 100.0 M.W. = 260 266 and 288 by cryoscopic methods, 264 by titration. The following salts have been analysed:— Acid Ammonium Salt—(C16H20O3)2, NH3, H2O.—This salt is sparingly soluble in water; it is readily obtained by saturating a solution of ammonia with the acid, filtering at once, and gently warming the filtrate. Calculated. Found. NH3 + H2O = 6.7 6.3 NH3 = 3.14 3.0 Barium Salt—(C16H20O3)2, Ba, 14 H2O.—This most characteristic crystalline salt. separates in well-developed square plates when a solution of barium-chloride is added to a solution of the acid in excess of ammonia. Three preparations gave—

Calculated. Found. I. II. III. H2O = 27.7 27.7 27.1 27.7 Ba = 15.1 15.8 15.3 15.1 Silver Salt—C16H20O3, Ag.—An amorphous flocculent precipitate prepared from a solution of the barium salt. Calculated. Found. Ag = 29.0 29.0 and 29.7 Benzoyl Rimuic Acid.—This compound was prepared by shaking the alkaline solution of rimuic acid with excess of benzoyl-chloride. It is sparingly soluble in cold alcohol; from hot alcoholic solutions it separates on rapid cooling as a transparent jelly, which becomes crystalline on standing. Calculated for C15H18O, C6H5CO, CO2H. Found. C = 75.8 75.6 H = 6.6 6.6 Rimuic acid boils at 296°–300° at 21 mm. By continued heating at 300° it loses water, and is converted into a colourless compound which is no longer soluble in alkalis, ether, or the usual organic solvents, and cannot be distilled without decomposition. Rimuic acid does not yield an ethereal salt when treated with absolute alcohol and hydrochloric-acid gas. It readily forms two crystalline nitro-acids and a sulphonic acid, which will be described in a later paper. It is of interest to note that Podocarpus cupressinum, a tree occurring in Java, contains as the chief constituent of its heart-resin an acid (podocarpic acid) which is so similar to rimuic acid that the two compounds might readily be mistaken for one another. Upon comparison it becomes clear that the two acids belong to the same homologous series—CnH2n−8OH, CO2H. Rimuic Acid, Podocarpic Acid, C16H20O3. C17H22O3. M.P. 192–193° C. 186–188° C. [a]d −150° + 136° The acids differ in the number of, molecules of water with which their salts crystallize. The following points of resemblance are remarkable: Both yield sparingly soluble acid ammonium salts which crystallize with one molecule of water. Both yield anhydrides when heated to 300° C. Both yield crystalline mono and dinitro derivatives the acid salts of which are yellow, the normal salts scarlet, or crimson. The dinitro derivatives are peculiarly sensitive to the action of light. Both acids, again, dissolve readily in cold concentrated sulphuric acid, and yield sulphonic acids the barium salts of which are sparingly soluble and highly

crystalline. Upon diluting the crude sulphuric-acid solution with water the smell of valeric acid is in each case distinctly perceptible. The solution of either of the sulphonic acids when warmed with very dilute nitric acid gives a yellow precipitate, the formation of which may be used as a test for nitric acid.