| Oenanthyl '' | CH3.(CH2)5.CHO |155 deg. | |
| Capric '' | CH3.(CH2)8.CHO |121 deg. | |
| Lauric '' | CH3.(CH2)10.CHO | |44.5 deg. |
| Myristic '' | CH3.(CH2)12.CHO | |52.5 deg. |
| Palmitic '' | CH3.(CH2)14.CHO | |58.5 deg. |
| Stearic '' | CH3.(CH2)16.CHO | |63.5 deg. |
|--------------------|-----------------------------------|---------|--------|
| Acrolein | | | |
| ally aldehyde | CH2 : CH.CHO | 52 deg. | |
| Crotonic '' | CH3.CH : CH.CHO |104 deg. | |
| Tiglic '' | | | |
| (guaiacol) | CH3.CH : C.CH3.CHO |116 deg. | |
|--------------------|-----------------------------------|---------|--------|
| Proargylic A. | CH : C.CHO | 59 deg. | |
|--------------------|-----------------------------------|---------|--------|
| Benzaldehyde | C6H5.CHO |179 deg. | |
| {o | |200 deg. | |
| Toluicaldehyde{m | C6H4.CH3.CHO |199 deg. | |
| {p | |204 deg. | |
| Cumic '' | C6H4.C3H7.CHO |235 deg. | |
| Cinnamic '' | C6H5.CH : CH.CHO |247 deg. | |
|____________________|___________________________________|_________|________|
For formaldehyde see FORMALIN. Acetaldehyde, CH3.CHO,
was first noticed by C. Scheele in 1774 and isolated and
investigated by J. v. Liebig (Annalen, 1835, 14, p.
133). It is prepared by oxidizing ethyl alcohol with dilute
sulphuric acid and potassium bichromate, and is a colourless
liquid of boiling point 20.8 deg. C., possessing a peculiar
characteristic smell. Its specific gravity is 0.8009 (0 deg.
C.). It is miscible in all proportions with alcohol, ether and
water. It is readily polymerized, small quantities of
hydrochloric acid, zinc chloride, carbonyl chloride, &c.
converting it, at ordinary temperatures, into paraldehyde,
(C2H4O)3, a liquid boiling at 124 deg. C. and of specific
gravity 0.998 (15 deg. C.). Paraldehyde is moderately soluble in
water, and when distilled with sulphuric acid is reconverted
into the ordinary form. Metaldehyde, (C2H4O)3, is produced
in a similar way to paraldehyde, but at lower temperatures
(e.g. in presence of a freezing mixture). It is a crystalline
solid, which sublimes at 112 deg. -115 deg. C. It is insoluble
in water, and is only slightly soluble in alcohol and
ether. When heated in a sealed tube at 120 deg. C. it is
completely converted into the ordinary form. Paraldehyde
is oxidized by dilute nitric acid, with formation of much
glyoxal, (CHO)2. (For trichloracetaldehyde see CHLORAL.)
By the action of acetaldehyde on alcohol at 100 deg. C.,
acetal, CH3.CH(OC2H5)2, is produced. It may also be
prepared by oxidizing ethyl alcohol with manganese dioxide
and sulphuric acid (A. Wurtz). It is a colourless liquid
of specific gravity 0.8314 (20 deg. /4 deg. ) (J. W. Bruhl) and
boiling point 104 deg. C. Dilute acids readily transform it
into alcohol and aldehyde, and chromic acid oxidizes it to
acetic acid. Chlor- and brom-acetals have been described.
Thioaldehydes are also known, and are obtained by leading
sulphuretted hydrogen into an aqueous solution of acetaldehyde.
By this means a mixture is obtained which by distillation
or the action of hydrochloric acid yields trithioaldehyde,
(C2H4S)3. For the constitution of these substances
see E. Baumann and E. Fromm (Berichte, 1891, 24, p.
1426). Aldehyde ammonia, CH3.CH(OH).NH2, is formed
when dry ammonia gas is passed into an ethereal solution of
acetaldehyde. It crystallizes in glistening rhombohedra,
melting at 70 deg. -80 deg. C., and boiling at 100 deg. C. It is completely
resolved into its components when warmed with dilute acids.
The higher aldehydes of the series resemble acetaldehyde
in their general behaviour. Unsaturated aldehydes are also
known, corresponding to the olefine alcohols; they show the
characteristic properties of the saturated aldehydes and
can form additive compounds in virtue of their unsaturated
nature. The simplest member of the series is acrolein, C3H4O
or CH2 : CH.CHO, which can be prepared by the oxidation
of allyl alcohol, or by the abstraction of the elements of
water from glycerin by heating it with anhydrous potassium
bisulphate. It is also produced by the action of sodium on
a mixture of epichlorhydrin and methyl iodide, C3H5OCl +
CH3I + 2Na = C3H4O + NaI + NaCl + CH4. It is a colourless
liquid, with a very pungent smell, and attacks the mucous
membrane very rapidly. It boils at 52.4 deg. C. and is soluble in
water. It oxidizes readily: exposure to air giving acrylic
acid, nitric acid giving oxalic acid, bichromate of potash
and sulphuric acid giving carbon dioxide and formic acid.
It combines with bromine to form a dibromide, from which E.
Fischer, by the action of baryta water, obtained the synthetic
sugars a- and b-acrose (Berichte, 1889, 22, p. 360).
Metacrolein, (C3H4O)3, is a polymer of acrolein. By passing
acrolein vapour into ammonia, acrolein ammonia, C6H9NO, is
obtained. It is a reddish amorphous mass, insoluble in
alcohol, and when distilled yields picoline (methyl pyridine)
(A. Baeyer, Ann., 1870, 155, p. 283). Citronellal, rhodinal
and geranial are also unsaturated aldehydes (see TERPENES.)
The aromatic aldehydes resemble the aliphatic aldehydes in most
respects, but in certain reactions they exhibit an entirely
different behaviour. They do not polymerize, and in the
presence of caustic alkalies do not resinify, but oxidize
to alcohols and acids (see BENZALDEHYDE for Cannizzaro's
reaction). When heated with alcoholic potassium cyanide
they are converted into benzoins (q.v..) Vanillin does
not give the Cannizzaro reaction, but with alcoholic potash
forms vanillic acid, HOOC(1).C6H3.OCH3 (3).OH(4), and
vanilloin. With ammonia, benzaldehyde does not form an aldehyde
ammonia, but condenses to hydrobenzamide, ( C6H5CH)3N2,
with elimination of water. Cumic aldehyde (cuminol),
(CH3)2CH(1)C6H4.CHO(4), is found in Roman caraway oil and
in oil of the water hemlock. It is a liquid, boiling at 235 deg.
C., and has a specific gravity of 0.973. On distillation with
zinc dust it forms cymene (1.4 methyl isopropyl benzene).
Salicylic aldehyde (ortho-hydroxybenzaldehyde), HO(1).
C6H4.CHO(2), an aromatic oxyaldehyde, is a colourless liquid
of boiling point 196 deg. C. and specific gravity 1.172 (15 deg. ).
It is found in the volatile oils of Spiraea, and can be obtained
by the oxidation of the glucoside salicin, (C13H18O7),
which is found in willow bark. It is usually prepared by the
so-called ``Reimer'' reaction (Ber., 1876, 9, p. 1268), in which
chloroform acts on phenol in the presence of a caustic alkali,
C5H5OH + CHCl3 + 4KHO = 3KCl + 3H2O + KO.C6H4.CHO,
some para-oxybenaldehyde being formed at the same time. It
is volatile (para-oxybenzaldehyde is not) and gives a violet
coloration with ferric chloride. For dioxybenzaldehydes
and their derivatives see PIPERONAL and VANILLIN.
Cinnamic aldehyde (b-phenyl acrolein), C6H5.CH : CH.CHO,
an unsaturated aromatic aldehyde, is the chief constituent of
cinnamon oil. It is prepared by oxidizing cinnamyl alcohol, or
by the action of sodium ethylate on a mixture of benzaldehyde and
acetaldehyde. It is a colourless aromatic-smelling oily liquid,
which boils at 247 deg. C. and readily oxidizes on exposure.
By condensation of aldehydes with pyruvic acid and
naphthylamines, the a-alkyl-naphthoquinoline-g-carboxylic
acids are produced; the same reaction takes place with the
aromatic amines generally (O. Doebner, Ann. 1804, 281, p. 1),
COOH
|
/ \ COOH / \ / \
| | + | + R.CHO = | | | + 2H2O + 2H.
\ / \NH2 CO.CH3 \ / \N/ \R
ALDEN, JOHN (1599?-1687), one of the ``Pilgrims'' who in
1620 emigrated to America on the ``Mayflower'' and founded
the Plymouth Colony. According to William Bradford's
History of the Plimoth Plantation, he was hired as a
cooper at Southampton, ``where the ship victuled,'' just
before the voyage, ``and being a hopfull yong man, was much
desired.'' He was one of the first settlers of Duxbury,
Massachusetts, where he lived during the greater part of his
life, and from 1633 until 1675 he was an ``Assistant'' to
the governor of the colony, frequently serving as acting
governor. At the time of his death, at Duxbury, on the
12th of September 1687, he was the last male survivor of
the signers of the ``Mayflower Compact'' of 1620, and with
the exception of Mary Allerton was the last survivor of the
``Mayflower'' company. He is remembered chiefly because of
a popular legend, put into verse as The Courtship of Miles
Standish by Henry W. Longfellow, concerning his courtship
of Priscilla Mullins, whom he married in 1623, after having
wooed her first on behalf of his friend, Miles Standish.
ALDER, a genus of plants (Alnus) belonging to the order
Betulaceae, the best-known of which is the common alder (A.
glutinosa.) The genus comprises a few species of shrubs or
trees, seldom reaching a large size, distributed through
the North Temperate zone, and in the New World passing
along the Andes southwards to Chile. The British species
A. glutinosa is confined to the Old World. This tree
thrives best in moist soils, has a shrubby appearance, and
grows under favourable circumstances to a height of 40 or 50
ft. It is characterized by its short-stalked roundish leaves,
becoming wedge-shaped at the base and with a slightly toothed
margin. When young they are somewhat glutinous, whence the
specific name, becoming later a dark olive green. As with
other plants growing near water it keeps its leaves longer
than do trees in drier situations, and the glossy green foliage
lasting after other trees have put on the red or brown of
autumn renders it valuable for landscape effect. The stout
cylindrical male catkins are pendulous, reddish in colour
and 2 to 4 in. long; the female are smaller, less than an
inch in length and reddish-brown in colour, suggesting young
fir-cones. When the small winged fruits have been scattered the
ripe, woody, blackish cones remain, often lasting through the
winter. The alder is readily propagated by seeds, but throws
up root-suckers abundantly. It is important as coppice-wood
on marshy ground. The wood is soft, white when first cut and
turning to pale red; the knots are beautifully mottled. Under
water the wood is very durable, and it is therefore used for
piles. The supports of the Rialto at Venice, and many buildings
at Amsterdam, are of alder-wood. Furniture is sometimes made
from the wood, and it supplies excellent charcoal for gunpowder.
The bark is astringent; it is used for tanning and dyeing.
ALDER-FLY, the name given to neuropterous insects of the family
Sialidae, related to the ant-lions, with long filamentous
antennae and four large wings, of which the anterior pair is
rather longer than the posterior. The females lay a vast number
of eggs upon grass stems near water. The larvae are aquatic,
active, armed with strong sharp mandibles, and breathe by
means of seven pairs of abdominal branchial filaments. When
