A Manual of the Chemistry of the Carbon Compounds

270 THE CMEMISTHY OF
Mtthglcrotonk Acid.—This isomeride of angelic acid is produced by
the action of phosphorus trichloride upon ethyl ethomethoxalate; it
crystallizes in needles, melting at 6*2°, When it is fused with caustic
potash it yields the same products as angelic acid, the constitution of
the two acids beiug as follows:—
Angelic Acid. Jletliylorotonio Acid.
CHg CH3
CH8
g 3 8
i CH
I
C-CII,
An acid having the same composition, called Hylic acid, has been
found in croton-oil; it melts at 64° and boils at 201°. The action of
caustic potash on this body has not yet been tried; it is' probably
identical with inethylcrotouic acid, both having the same meltingpointy
and both their ethyl-ethers boiling at 156°.
PyrotereUc Add CpH10O^ has been obtained by the distillation of
terebic acid C7H10O4 fan oxidation-product of oil of turpentine). It
is a liquid boiling at 210°, and smelling lika butyric acid. It is
isomeric with ethylerotonic acid, which has been prepared from ethyl
ethoxalate, and crystallizes in quadratic prisms melting at 39°*5. By
the action of caustic potash, both acids yield acetic acid and butyric
acid.
Gimme Add C^H^Oj, a crystalline solid melting at 44°, and having
a rancid odour, is contained in a kind of tree-bug (Rhaphigaster
jmnctipe/Mm).
Hypogcek Acid or PhysetoUic Acid CmH^Og occurs aa glycerid
together with palmitic and aracbidic acids, in the oil of the earth-nut
(Arachis hypogem), and in the oil contained in the oavities of the
head of the sperm-whale (Physeter macroeephalus). It crystallizes in
colourless needles, melting at 34°. In contact with the air it absorbs
oxygen, and assumes a yellow colour and a rancid smelL Nitric, trioxide
converts thia acid into an isomerio (or polymeric modification)
called gaitlic acid, a crystalline colourless mass, which melts at 38°,
and remains unaltered in the air. ,-
Both acids combine with one molecule m bromine. By heating
these brominated ncids with alcoholic potash-solution to 170° they lose
hydrobromic acid and are converted into palinitolic aeid O^H^Oj,
crystallizing in silky needles melting at 42°. This acid readily combines
with one or two molecules of bromine, but apparently not
with hydrogen. On oxidizing it with fuming nitric acid a part ia
converted into palmiioxylic acid CuHgO^ a monobasio acid crystallizing
in colourless plates melting at 67°. Another portion is further
oxidized to suberic a-cit au-l mdhrir nldeliydc C8HUOS, a yellow
oily lu|iii't.