A Manual of the Chemistry of the Carbon Compounds

THE CARBON COMPOUNDS. 261
ALLYL-COMPOVNDS.
These compounds contain the radical cdlyl GgHg, which differs from
propenyl by being a monad radical, two of the carbon atoms being
linked together by two of the combining units of each. The same
of this radical is derived from the fact that some of its compounds
occur in AUium-speeka (garlic, &u.). The allyl-compounds combine
with hydrogen, chlorine, &c, yielding thus either propyl- or propenyl
compounds.
Allyl Alcolwl CjBLOH.—When a mixture of glycerin and
crystallized oxalic acid is heated, carbon dioxide is evolved, and at
about 100° dilute formic acid begins to distil over; by raising the
temperature the evolution of carbon dioxide ceases, but begins again
at 190°, and a mixture of allyl alcohol and other products distils.
Monoformin is formed, which at a lower temperature is acted upon by
water, yielding formic acid and glycerine, whilst at a higher temperature
it is resolved into allyl alcohol, carbon dioxide, and water :—
(OH
G3H6 -j OH = CgHj.OH + CO8 + HaO
(O.COH
To obtain pure allyl alcohol the product is treated with caustic
potash, distilled again, and rectified over anhydrous baryta. It is a
limpid liquid, boiling at 97°, and possessing a characteristic pungent
smell (like most allyl-compounds).
When allyl alcohol is oxidized with dilute chromic acids, it yields
formio acid, but no acetic acid, showing that it does not contain the
group OHj, but has the constitution CH,=CH—CH2.OH.
Allyl alcohol does not combine readily with hydrogen; it is not
changed by acting with sodium amalgam or zinc and hydrochloric
acid on its aqueous solution. But when it is heated with ag equal
weight of oausiao potash in a flask connected with a reversed condenser,
an evolution of hydrogen commences at 105°, and goes on up to.
155°. On distilling the solid mass thus obtained with water, a mixture
of ethyl alcohol and propyl alcohol (about 20 per cent, of the allyl
alcohol employed) is obtained, and the residue contains potassium
formate, and salts of other acids.
Allyl alcohol readily combines with chlorine, forming dichloropropyl
alcohol, a liquid boiling at 182°, which is isomeric with dichlorljydrin;—
Diehlorhydrin. Dichloropropyl Alcohol.
OH8C1
IH.OH CHC1
!H2.C1