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y Winkler, Ecpcrt. Pharm. Ixvii. 1, 56.

4 Jahresb. Chcm. iv. 519. 6 Loc. cit. ; Ittner, ibid. xxiv. 395.

6 Ann. CJiem. Pharm. Ixxxv. 183. 7 Miiller ami Limpricht, ibid. cxi. 136.

K 2



AROMATIC COMPOUNDS.



orphenylhydroxyacetic acid, C 6 H 5 .CH(OH)C0 2 H, the formation of
which, however, cannot be taken as a proof of the presence of the
nitril, for this acid is also formed when a mixture of hydrochloric
acid, hydrocyanic acid and benzaldehyde, is heated to boiling.
Fileti, however, supplied the proof by showing that phenyl-
ethylamine, C 6 H 5 .CH 2 .CH 2 .NH 2 , is formed by the action of zinc
and hydrochloric acid on an alcoholic solution of crude oil of
bitter almonds or of the cherry-laurel, while a mixture of benz-
aldehyde and hydrocyanic acid subjected to the same treatment
yielded methylamine. 1

2086 Oil of bitter almonds is prepared on the large scale "by
distilling the pressed residue of bitter almonds with water. In
order to get all the amygdalin into solution and obtain the
best yield of oil, Pettenkofer brings 12 parts of the roughly
powdered mass into 100 120 parts of boiling water, keeps it at
the boiling-point for 1 5 30 minutes, and after cooling adds 1
part of the powder stirred up with 6 7 parts of water, and
then rapidly distils. 2 The aqueous distillate contains some oil in
solution, which is removed by a subsequent distillation.

Pettenkofer obtains a yield of O'O per cent, of oil of bitter
almonds on the pressed residue, while on the large scale the
yield is in this way 074 1'67 per cent, or 0'42 0'95 parts in
100 of bitter almonds. The great variation in these numbers is
partly accounted for by the varying amounts of amygdalin
present, but is also due to the admixture of sweet almonds 3

Some manufacturers free the oil from hydrocyanic acid ; the
purified oil, however, oxidizes much more readily than when in
the crude state, so that others add hydrocyanic acid and warm
gently 4 in order to make it keep better, the nitril, which will be
described under Phenylhydroxyacetic acid, being formed.

Oil of bitter almonds is chiefly employed in perfumery, and
as a flavouring, for which, however, it must be used with care.
Extracts of bitter almonds and of cherry-laurel are used in
medicine.

Benzaldehyde can be obtained in many other ways, some of
which have been already mentioned under the benzyl com-
pounds. Dumas and Peligot obtained it by oxidation of cinnamic
acid, C 6 H 5 .CH CH.C0 2 H; 5 Miiller prepared it in a similar

1 Gaz. Chim. Itnl. viii. 446. 2 Ann. Chcm. Pharm. cxxii. 77.

3 Fliickiger and Hanbury, Pharmacographia, 2nd ed. 250.

4 Dusart, Bull. Soc. Chim. [2] viii. 459.

5 Ann. CJiem. Pharm. xiv. 385.



PREPARATION OF BENZALDEHYDE.



manner from oil of cinnamon, which contains cinnyl alde-
hyde, 1 arid Toel from, styrone or cinnyl alcohol, C 6 H 5 .CH
CH.CH.,.OH. 2 Various other allied aromatic compounds yield
benzaldehyde on oxidation. Cannizzaro showed that it is the
first product of the oxidation of benzyl alcohol (p. 91), while
Guckelberger and Keller found it among the products which are
formed by the action of potassium permanganate and sulphuric
acid on the albuminoids. 3

It is readily obtained from benzoic acid by reduction carried
on in aqueous solution by means of sodium amalgam, 4 or by
heating with stannous oxide. 5 Baeyer obtained it by passing
the vapour of benzoic acid or of phthalic acid, C 6 H 4 (C0 2 H) 2 , over
heated zinc-dust 6 and Chiozza by the action of copper hydride
on benzoyl chloride. 7 Piria found that it is formed by distilling
a mixture of calcium benzoate and formate. 8

When the vapour of benzene or toluene, mixed with air, is
brought into contact with a glowing spiral of platinum or palla-
dium, benzoic acid is formed together with some benzaldehyde,
which is formed in larger quantity from xylene (dimethylbenzene)
or cymene (methylpropylbenzene.) 9 Toluene, as already men-
tioned (p. 6), forms a compound with chromium oxychloride,
which is decomposed by water with formation of benzaldehyde.

This is also formed when benzyl chloride is boiled with dilute
nitric acid or water and lead nitrate, 10 as well as by heating
benzidene chloride, C 6 H 5 .CHC1 2 , with silver oxide, mercuric
oxide, 11 or alcoholic potash, 12 or with water to 140 160 . 13 When
this compound is heated with two molecules of sulphuric acid
to 30, hydrochloric acid is evolved and a syrupy liquid formed,
which is decomposed by water into sulphuric acid and benz-
aldehyde. 14

On the small scale benzaldehyde is best prepared by gradually
heating benzidene chloride to 130 with the necessary amount
of anhydrous oxalic acid :

C a H 5 .CHCl 2 + C 2 H 2 4 = C 6 H 6 .CHO + CO + CO 2 + 2HC1.

Journ. Prakt. Chem. xviii. 385. 2 Ann. Chem. Pharm. Ixx. 5.

Ibid. Ixiv. 60 ; Ixxii. 86. Kolbe, ibid, cxviii. 122.

Dusart, Compt. Rend. Iv. 448. 6 Ann. CJicm. Pharm. oxl. 29fl.

ibid. Ixxxv. 232. 8 Ibid. c. 105.

Coquillon, Compt. Rend. Ixxvii. 444 ; Ixxx. 1089.
1 Grimaux and Lauth, Bull. Soc. Chim. [2] vii. 106.
1 Gerhardt, TraiU Chim. iv. 721.
1 Cahours, Ann. Chem. Pharm. Suppl. ii. 253.

13 Limpricht, ibid, cxxxix. 319.

14 Oppenlteim, Bcr. Deutsch. Clwm. Gcs. ii. 213.



134 AROMATIC COMPOUNDS.



The residue is distilled under diminished pressure, and the
aldehyde purified by a single rectification. 1

2087 Benzaldehyde is manufactured by boiling 2 parts of
benzyl chloride with 3 parts of lead nitrate, or better, copper
nitrate, and 10 parts of water for several hours in an apparatus
connected with an inverted condenser, the operation being
conducted in a current of carbon dioxide ; half the liquid
is then distilled off, and the oil separated from the water.
It is obtained from benzidene chloride by heating it under
pressure in an iron vessel with caustic soda. According
to Espenschied it is possible to heat without pressure in an
apparatus connected with an inverted condenser if milk of lime
be used, or if whitening, or some other finely-divided insoluble
substance, be added and the whole stirred into an emulsion,
which boils at a higher temperature and thus, facilitates the
decomposition of the chloride. Jacobsen recommends a process
in which benzidene chloride is heated with glacial acetic acid and
zinc chloride, benzaldehyde and acetyl chloride being formed ;
the necessary amount of water is then allowed to flow in, and
the acetic acid which is formed, recovered. 2

The benzaldehyde thus obtained, which always contains
chlorine compounds, is used in the colour industry. The pure
compound may be obtained from it by preparing the double
sulphite, which has already been mentioned, and decomposing
this with caustic soda solution.

Properties. Benzaldehyde is a colourless, strongly refractive
liquid which has a well known characteristic smell and a burn-
ing aromatic taste. It dissolves in more than 300 parts of water ; 3
boils at 179, and has a specific gravity of T0636 at and of
T0504 at 15. In the pure state it rapidly oxidizes in the air and
is also oxidized by boiling with chromic acid solution, manganese
dioxide and sulphuric acid, or freshly precipitated ferric oxide. 4
It is, however, only slowly attacked by strong, boiling nitric acid ;
the red, fuming acid only yields benzoic acid, but when mixed
with sulphuric acid gives substitution products. 5 It differs
from the aldehydes of the fatty series in not reducing an alkaline
copper solution. 6



1 Anschiitz, Ann. diem. Pharm. ccxxvi/18.

Ber. Deutsch. Chcm. Ges. xiii. 2013 ; xiv 1425

Fluckiger, Jahresb. Chcm. 1875, 182.
4 Grager, Ann. Chem. Pharm. cxi. 124

Lippmann and Hawliczek, Ber. Deutsch. Chem. Ges. ix. 1463.

lollens, ibid. xiv. 1950.



BENZALDEHYDE. 136



It is converted into benzyl alcohol by treatment with sodium
amalgam and water; hydrobetizoin is simultaneously formed,
together with the isomeric isohydrobenzoin C 14 H 12 (OH) 2 , which
compounds, together with benzoin, C 6 H 5 .CH(OH)CO.C 6 H 5 ,
obtained by heating benzaldehyde with alcoholic potassium
cyanide solution, will be subsequently described.

Benzaldehyde is not poisonous; when taken internally it
appears in the urine as hippuric acid; 1 it is not decomposed
when heated to dull redness, but is decomposed, chiefly into
benzene and carbon monoxide, when passed through a tube
filled with pumice stone and heated to bright redness. 2

Benzaldehyde readily combines with other carbon compounds
with elimination of water and is therefore largely employed,
both on the small and large scale, for the synthesis of con-
densation products, which will be subsequently described. Only
a few of the most important reactions will be mentioned here.

(1.) When benzaldehyde is heated with sodium acetate and
acetic anhydride, cinnamic acid, C 6 H 5 .CHrzCH.CO 2 H, is formed.
The homologues of this acid are prepared in an analogous
manner from the other fatty acids.

(2.) Aromatic ketones are easily obtained by the con-
densation of a fatty ketone with benzaldehyde; thus ordinary
acetone yields methylcinnyl ketone, CH 3 .CO.CH=CH.C 6 H 5 ,
which is converted by the further action of benzaldehvde into
dicinnyl ketone or cinnamone, CO(CH=CH.C 6 H 5 ) 2 .

(3.) When benzaldehyde is heated with aniline and zinc
chloride, diamidotriphenylmethane, C 6 H 5 .CH(C 6 H 4 .NH 9 ) 2 , is
obtained ; if dimethylaniline be employed, the base, C 6 H 5 .CH
(C 6 H 4 .N.(CH 3 ) 2 ) 2 , is formed, and this yields on oxidation the
colouring matter known as benzaldehyde-green or malachite-
green.

(4.) Benzaldehyde combines with the nitroparaffins to form
aromatic nitro-olefines, such as Dhenylnitro-ethylene, C 6 H 6 .
CH CHN0 2 , etc.

1 Frerichs and Wohler, Ann. Clum. Pharm. Ixv. 337.
- Barreswill aiid Boudault, ibid. Hi. 360.



136 AROMATIC COMPOUNDS.



BENZIDENE COMPOUNDS.

2088 Benzaldehyde, like other aldehydes, behaves as the
oxide of a dyad radical, which is called benzylene, benzylidene
or benzidene. As in all analogous cases, the corresponding
alcohol cannot be prepared, but ethers, ethereal salts, and
other derivatives are known.

Benzidene dietfiyl ether, C 6 H 5 .CH(OC 2 H 5 ) 2 , was obtained
by Wicke by the action of benzidene chloride on sodium
othylate. It is a liquid which possesses a pleasant smell
resembling that of the geranium, and boils at 222. Wicke
has also prepared various other ethers. 1

Benzidene dicUoride, C 6 H 5 .CHC1 2 . Cahours prepared this
compound by the action of phosphorus peutachloride on oil
of bitter almonds 2 and named it chlorobenzol, a name
which was subsequently changed into chloride of oil of bitter
almonds and finally into benzal chloride (benzaldehyde chloride),
which is still employed.

It is also obtained by treating benzaldehyde with carbonyl
chloride or succinyl chloride : 3

/CCU /COv

C 6 H 6 .CHO + C 2 H 4 / \ = C 6 H 6 .CHC1 2 + C 2 H 4 / \0.

It is, however, most readily prepared by passing chlorine
into boiling toluene until it has gained 75 per cent, in weight
and then purifying the product by fractional distillation. 4

It is a colourless liquid which boils at 206 207 and
has a specific gravity of T295 at 16. 5 In the cold it has only
a feeble smell, but when heated it gives off a penetrating
vapour which produces a flow of tears. It is manufactured
and employed for the preparation of benzaldehyde.

Benzidene dibromide, C 6 H 5 .CHBr 2 , is formed by the action of
phosphorus pentabromide on benzaldehyde; it is a powerfully

Wicke, Ann. Chem. Pharm. cii. 363.

Ann. Chim. Phys. [3] xxiii 329.

Rembold, Ann. Chem. Pharm. cxxxviii. 189.

Beilstein and Kuhlberg, ibid, cxlvi. 322.

Hubner and Bente, Ber. Deukch. Chem. Ge*. vi. 804






BENZIDENE COMPOUNDS. 137

refractive liquid, which can only be distilled without decomposi-
tion under considerably reduced pressure. 1

Benzidene di-iodide, C 6 H 5 .CHI 2 . Geuther and Cartmell, by
the action of hydriodic acid gas on benzaldehyde, obtained a
peculiar compound, which they named benzaldehyde oxyiodide,
C 21 H 18 I 4 O ; it forms colourless, rhombic tablets, which melt at
28 and rapidly become coloured dark in the light. It smells
exactly like cress, and can be volatilized with steam, yielding
a vapour which attacks the eyes and nose most violently, the
pain caused being greater and more enduring than that pro-
duced by acrolein. When it is heated with silver nitrate solution,
a smell of benzaldehyde is produced. 2

The constitution of this body, the formula of which can be
expressed as C 6 H 5 .CHO + 2C H 5 .CHI 2 , is unknown.

Benzidene diacetate, C 6 H 5 .CH(C 2 H 3 O 2 ) 2 . Wicke obtained this
compound by the action of silver acetate on berizidene chloride ; 3
it is also formed when benzaldehyde is heuted with acetic
anhydride, 4 and crystallizes from ether in small, monoclinic
tablets or in twins, which have the swallow-tail form of crystals
of gypsum. It melts at 45 46, 5 and boils at 220 . 6

Wicke has also prepared some other ethereal salts of
benzidene.

Potassium benzidene sulphite, C 6 H 5 .CH(OH)S0 3 K. This
compound, which was earlier called the bisulphite of benz-
aldehyde-potash, was obtained by Bertagnini in crystals by
agitating benzaldehyde with a concentrated solution of acid
potassium sulphite. 7 It crystallizes from hot, dilute alcohol in
long plates, which are slightly soluble in cold alcohol, readily in
water, but are almost insoluble in a concentrated solution of acid
potassium sulphite. It is decomposed by simply boiling with
water, more readily by acids or alkalis, with separation of benz-
aldehyde, which can thus be obtained pure (p. 134).

Sodium benzidene sulphite, C 6 H 5 .CH(OH)S0 3 Na + H 2 O, forms
small crystals, and behaves like the potassium salt.

Ammonium benzidene sulphite, C 6 H 5 .CH(OH)S0 3 NH 4 + H 2 O.
Bertagnini, on shaking benzaldehyde with a concentrated solu-
tion of acid ammonium sulphite, observed an evolution of heat
and obtained a clear solution from which no crystals separated out.

1 Michaelson and Lippmann, Ann. CJiem. Pharm. Suppl. iv. 113.

2 Ann. Chem. Pharm. cxii. 20. ' Ibid. cii. 368.

4 Geuther, ibid. cvi. 251 ; Hrtbner, Zeitschr. Chem. 1867, 277.

5 Perkin, ibid. 1868, 172.

6 Neuhof, Ann. Chem. Pharm. cxlvi. G23. 7 Ibid. Ixxxv. 183.



138 AROMATIC COMPOUNDS.

Otto, however, obtained the compound in crystals by mixing
alcoholic solutions of sulphur dioxide and hydrobenzamide ; a
precipitate is formed consisting of microscopic needles which are
slightly soluble in alcohol, readily in water, and separate from
the latter in transparent crystals containing three molecules of
water. 1

Benzaldehyde does not form an analogous compound with
acid aniline sulphite, but a very stable substance of the
empirical formula, 2C 7 H 6 O + 2C 6 H 7 N + SO 2 , is produced, and
crystallizes from water in long, flat needles. 2

Benzidene sulphide, C H 5 .CHS. Cahours prepared this com-
pound by heating benzidene chloride with an alcoholic solution
of potassium hydrosulphide and named it sulphobenzene. 3 It
was then further investigated by Fleischer 4 and Bottinger. 5 It
crystallizes from hot alcohol in nacreous plates and from ether in
transparent, four-sided prisms, melting at 70 71. On .heating
with caustic potash it yields benzyl hydrosulphide, benzyl
disulphide and some benzoic acid, and on dry distillation
gives stilbene, C 14 H 12 , tolallyl sulphide, C 14 H 10 S, and thionessal,
C 28 H 20 S. (Seep. 106.)

Pardbenzidene sulphide, (C 6 H 5 .CHS) n . By the action of am-
monium sulphide on an alcoholic solution of benzaldehyde,
Laurent obtained a compound of this composition, which he
called sulphobenzoyl hydride (hydrure de sulfobenzo'ile), and de-
scribed as a powder consisting of microscopic granules, which
became soft at 90 95, and, after careful fusion, solidified to
a transparent mass. It is odourless, but imparts to the hands a
very repulsive, adhering alliaceous odour. 6 On dry distillation it
yields the same products as benzidene sulphide.

The compound which Klinger obtained by passing sulphuretted
hydrogen into a solution of benzaldehyde in absolute alcohol and
named a-lenzothio-aldehyde, is probably identical with this body.
It is amorphous, softens at 80 85, and is converted by acid
chlorides into /B-lenzothio-aldehyde, which is slightly soluble in
alcohol, readily in hot glacial acetic acid, and crystallizes in
lustrous white needles, melting at 225 226. 7

This compound is most readily obtained by dissolving

1 Neuhof, Ann. Chcm. Pharm. cxii. 308.

- Schiff, ibid. cxl. 130 ; ccx. 128.

3 Ann. Chin. Phys. [3] xxiii. 333 ; Ann. Chtm. Pharm. Ixx. 40.

Ibid. cxl. 234. s SeTf j) eutli ch. Chcm. Ges. xii. 1053.

Ann. Chim. Phy*. [3] i. 292 ; Ann. Chcm. Pharm. xxxviii. 320 ; see also
Roclileder," ibid. xxxvr.. 346. 1 SeTm j) cutscht Chcmm Gcs . ix 1893 .



BENZALDOXIME. 139



amorphous benzothio-aldehyde in hot benzene and adding a small
quantity of iodine also dissolved in benzene ; lustrous needles of
the formula C 6 H 5 .CHS + C 6 H 6 soon separate out, which lose
benzene and become opaque at 125 ISO . 1

a-Benzothio-aldehyde is also formed, together with ammonia,
when an alkaline solution of benzothiamide, C 6 H 5 .CS.NH 2 , is
treated with sodium amalgam. 2

Both thio-aldehydes, when heated with copper dust, yield
stilbene, C U H 10 , as the chief product, and the amorphous com-
pound on fusion with caustic potash yields the same products as
benzideno sulphide (Bb'ttinger). Klinger was unable to convert
the latter, which he considered to be <y-benzothio-aldehyde, into
the /3-compound by the action of acetyl chloride or iodine ; the
/3-compound is probably a polymeric modification, and is best
called parabenzidene sulphide.

2089 Benzidcnoxime, or Benzaldoxime, C C H 5 .CH.NOH, is formed
when benzaldehyde and sufficient alcohol to form a clear
solution are added to an aqueous solution of hydroxylamine
hydrochloride containing an excess of sodium carbonate :

C 6 H 5 .CHO + H 2 N.OH - C 6 H 5 .CH=N.OH + H 2 O.

After twenty-four hours the mixture is extracted with ether
and the residue, after the evaporation of the ether, rectified.

Benzaldoxime is an oily liquid, which boils above 220 with
partial decomposition, and is decomposed by hydrochloric acid
into the substances from which it is formed. On treatment with
alcoholic caustic soda it gives the compound C 6 H 5 .CH.NONa,
which crystallizes from water in small, lustrous plates. By the
action of methyl iodide on this, the methyl ether, C 6 H 5 .CH,
NOCH 3 , is obtained as a light, oily liquid, which has a very
pleasant, fruity odour, and boils at 190 192; other ethers have
been prepared in a similar manner. 3

Hydrobenzamide, or Tribenzidcnediatnine, N 2 (CH.C H 5 ) 3 . Acet-
aldehyde combines directly with ammonia to form aldehyde
ammonia, CH 3 .CH(OH)NH 2 , but benzaldehyde behaves in a
completely different manner ; three molecules of the latter lose
all their oxygen, which combines with the hydrogen of two
molecules of ammonia, the place of this being taken by the
benzidene groups.

1 Ber. Deutsth. Chcm. Gcs. x. 1877.

2 Bemthsen, ibid. x. 36.

3 Tetraczek, ibid. xv. 2783 ; xvi. 823.



140 AROMATIC COMPOUNDS.

Hydrobenzamide is slowly formed when benzaldehyde is
allowed to stand in contact with aqueous ammonia ; x more
rapidly when the two are heated together. 2

Benzaldehyde absorbs dry ammonia, and if the product of this
absorption be allowed to stand in a vacuum, water is lost and
hydrobenzamide remains ; 3 it is also formed when benzidene-
dichloride is allowed to stand for some months with aqueous
ammonia. 4

It is readily soluble in alcohol and ether, and crystallizes in
lustrous, rhombic pyramids, melting at 110; very fine crystals
may be obtained by pouring an excess of aqueous ammonia on
to a mixture of equal volumes of benzaldehyde and ether, and
allowing the whole to stand. 5 It is tasteless, but its alcoholic
solution has, according to Laurent, a faint taste of burnt
almonds. On boiling with alcohol it slowly decomposes into
ammonia and benzaldehyde ; acids rapidly produce this decom-
position. On oxidation with aqueous chromic acid, a large
quantity of benzoic acid is formed (Fownes).

When it is boiled with caustic potash or heated to 120 130,
it is converted into the isomeric amarine, which will be sub-
sequently described ; the relation between the two compounds
is shown by the following formulee :

Hydrobenzamide. Amarine.

C 6 H 6 .CHrrNv C 6 H,.C.NH

CH.C 6 H 5 . |! >CN.C 6 H 5 .

C 6 H 5 .C.NH

Thiobenzaldine, (C 6 H 5 .CH) 3 S. 2 NH. Laurent obtained this
compound, the analogue of thialdine (Pt. II. p 83), by allowing
a mixture of crude oil of bitter almonds, ammonium sulphide
and ether, to stand for several weeks. It crystallizes in nacreous
plates or monoclinic prisms which melt at 125, and impart
an unpleasant smell to the skin. When it is boiled with
alcohol, sulphuretted hydrogen is given off, while alcoholic
potash decomposes it with evolution of ammonia. 6

Bcnzidene-aniline, C 6 H 5 .CH=zN.C 6 H 5 . Gerhardt and Laurent
obtained this compound by heating benzaldehyde with aniline,

1 Laurent (1836), Ann. Chim. Phys. Ixii. 23 ; Ixvi. 18 ; Ann. Chcm. Pharm.
*" 13 - 2 Rochleder, ibid. xli. 89.

Herzfeld, Ber. Deutsch. Chcm. Ges. x. 1271.

* Ann. Chcm. Pharm. xxxviii. 323.



4 Engelhardt, Ann. Chcm. Pharm. ex. 77.
6 Eckmann, ibid. cxii. 175.



CONDENSATION PRODUCTS OF BENZALDEHYDE. 141

and named it benzoylanilide. 1 The same compound is formed,
as shown by Schiff, when benzaldehyde is heated with thio-
carbanilide : 2

3CS(NHC 6 H 5 ) 2 + 6C 6 H 5 .CHO =
6C 6 H 5 .CH N. C 6 H 5 + CS 2 + 2C0 2 +H 2 S + 2H 2 O.

It is very soluble in alcohol and ether, separating from the
latter in warty crystals, and crystallizing from carbon disulphide
in yellow needles, which melt at 4*2, 3 and are volatile with steam.
It does not combine with acids, and is partially decomposed on
heating into benzaldehyde and aniline.

2090 Benzidene-aniline cyankydrate, C 6 H 5 .CH~N.C 6 H 5 .CNH.
Cech obtained this compound by the action of potassium cyanide
on an alcoholic solution of benzaldehyde and aniline or aniline
hydrochloride ; it is also formed when hydrocyanic acid is passed
into fused benzidene-aniline, and is decomposed into its com-
ponents by heat. It crystallizes from carbon disulphide in silky
needles, which melt at 82, sublime readily, and are volatile with
steam.

JBenzidenephenylhydrazone, CeH^CHrrN.NH.CeH^ is formed
by a violent reaction when benzaldehyde and phenylhydrazine
are brought together. It crystallizes from dilute alcohol in
monoclinic prisms, which melt at 152'5 and can be volatilized
without decomposition.

Benzidenediphcnylhydrazone, C 6 H f) .CH = NC.(C 6 H 5 ) 2 , forms
small yellow crystals, melting at 122 . 4

1'hcnylbenzaldehydine, or JBenzidene-ortJwdiamidobenzene, (C 6 H 5 .
CH=:N) 2 C 6 H 4 , is formed when a dilute aqueous solution of
orthodiamidobenzene hydrochloride is shaken up with benz-
aldehyde, the hydrochloride thus obtained being purified by
re-crystallization, and the base precipitated with caustic potash.

Phenylbenzaldehydine is insoluble in water and crystallizes
from alcohol in six-sided prisms, melting at 133 134.

Phenylbenzaldehydine hydrochloride, C 20 H 16 N 2 .HC1, crystallizes
in colourless prisms which are only slightly soluble in water, and
lose hydrochloric acid when their solution is boiled.

When the base is heated with ethyl iodide to 100 120, the
compound C.joHjgN.j.C.jHgl is formed; it crystallizes from hot
water in colourless, thick prisms, melting at 211 21 3. 5

1 Jahresb. Chcm. 1850, 488. 2 Ann. Chcm. Pharm. cxlviii. 336.

3 Cech, Bcr. Deutsch Chcm. Ges. xi. 246.

4 K. Fischer, Ann. Chcm. Pharm. cxc. 134, 179.

J Engelbrecht and Ladcnburg, Bcr. Deutsch. Chcm. Gcs. xi. 1653



142 AROMATIC COMPOUNDS.



Eenzideneparadiamidobcnzene, (C 6 H 5 .CH N) 2 C 6 H 4 , is formed
by the action of paradiamidobenzene on benzaldehyde ; it
crystallizes from alcohol in plates which have a silver lustre, and
melt at 140 ; it is decomposed by acids into its components,
since only the ortho-diamines form stable basic aldehydines l
(Part III. p. 7 2).

Benzidenedimethylparadiamidobcnzene, C 6 H 5 .CH N.C 6 H 4 .N
(OH 3 ) 2 , is readily formed by heating benzaldehyde with di-
methylparadiamidobenzene, and crystallizes from hot alcohol in
lustrous plates or needles, melting at 93. It is a feeble, di-acid
base. 2

Dibenzidcne-orthodiamidotolucne, or Tolulcnzaldeliydinc, (C 6 H 5 .
CH=N) 2 C 6 H 3 .CH 3 , has been obtained by Ladenburg from
orthodiamidotoluene ; it crystallizes in lustrous, monoclinic



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