Hugh McGuigan.

An introduction to chemical pharmacology: pharmacodynamics in relation to ... online

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the same effect.

The most prominent action of the methane group as a whole
is the anesthetic, hypnotic, and analgesic action. The members
of the benzene series on the other hand have a more pronounced
action on the motor side of the nervous system and are antiseptics.


(Sypnos— sleep) (An. without — algos — pain)
These may be divided into:

1. The chloroform group

2. The urethane group

3. The sulphone group

1. The Chloroform Group. — Chloroform, CHCI3, is formed by
the action of bleaching powder (a mixture of CaCl2 and CaOCl2)
on dilute alcohol or acetone. The chloroform is distilled off,
washed, and treated with concentrated H2SO4 to destroy other
derivatives, and is then rectified. The bleaching powder supphes
chlorine which is an oxidizing agent.

The reactions are complex, and probably as follows:

1. C2H6OH + CaOCla = CaCl2 + CH3CHO + H2O

2. 2CH3CHO + eCaOCU = 3CaCl2 + 3Ca(OH)2 + 2C2-


3. 2C2HCI3O + Ca(0H)2 = 2CHCI3 + Ca(CH0)2


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4. with acetone: >C0 + GCaOCla = 2CHC18 +

2Ca(OH2) + CaCCaHaOj), + CaCU


Chemical Tests

1. Place 2 cc. of chloroform in a dish and apply flame. Com-
pare with ether and alcohol.

2. Add a few drops of AgNOa to chloroform. No precipitate
if pure. Why? It contains chlorine. Make alkaline and again
heat. Compare with chloral.

3. Evaporate 10 cc. from filter paper on a clean glass sUde.
No odor or residue should remain, if pure.

4. A paper dipped in chloroform bums with a green mantle
and HCl is given off.

6. Test a few cc. of chloroform by boiling with a few drops of
KOH and 0.1 gram of resorcinol. The intense red color is due to
rosolic acid, a derivative of anilin. Chloral gives this same result.

Resorcinol C6H4(OH)2 1 : 3 .CHs

/ ^OH
RosoUc acid C— C6H4OH

C6H4 = O

In the presence of air, chloroform decomposes slowly into car-
bonyl chloride (phosgene) and HCl.

CHCls + = COCI2 + HCl.

The carbonyl chloride is very poisonous. To prevent decom-
position, it should be kept in the dark; and 1 per cent, alcohol
added as a preservative. The action of the alcohol is as follows:

<OC2H6 (ethyl carbonate)

OC2H6 + 2HC1

6. Chloroform is decomposed by passing its vapor through a
hot tube. HCl is formed which can be recognized by testing
with moist litmus paper, and by the precipitation of AgCl when
passed into silver nitrate solution.


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7. Phenyl Isocyanide Test. — Add 1-2 drops of aniline and a
few drops of aqueous KOH to the chloroform. Heat gently.
Phenyl isocyanide is produced. This has a characteristic in-
describable repulsive odor. The reaction is:

CHCls + CeHsNHa + 3K0H = CcHbNC + 3KC1 + SHjO

Chloral, chloralhydrate, bromof orm, iodoform, and carbon tetra-
chloride also give this test. The test is sensitive 1:6000.

8. Chloroform will reduce Fehling's solution.


Urethane: Ethyl carbamate CO^


Urea and alcohol under proper conditions yield urethane. —

/NH2 .NH2

C0\ + C2H50H->CO<

^NH2 ^OC2H6 + NHs

This is soluble in water, a weak hypnotic, and breaks down in
the body to its components, probably by the following mechanism :

/NH2 .NH2

C0<^ + NHs = C2H5OH + C(\

^OC^Es ^NH2

Nearly all substances in the body break down much more
readily into their components than they can be synthesized. In
the formation of urethane, indirect processes must be employed:

CO + 2C1 in sunlight->CO<Q carbonyl chloride

.Cl .Cl

C0<^ + C2H60H->CO<' + HCl.

Cl OC2HB chloroformic ester

/Cl /NH2

C0( + NH3->C0<( Urethane + HCl

^OCsHb ^OCaHs

It has been found that the pharmacologic action of the ure-
thanes, like the alcohols, increases with increased molecular
weight, and with the size of number of the alcohol radicals, con-


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sequently, diurethane, C(X^ is a more powerful narcotic,

than urethane.

Hedonal, C0<^ ^CHs which is the ester of


urea and the amyl alcohol methyl propyl carbinol, is more power-
ful than urethane. On account of both the urea and alcohol
content, these drugs are strongly diuretic.


Diethyl malonyl urea, is made from urea, alcohol and malonic
acid, by the introduction of esters of diethyl malonic acid with
urea in the presence of metallic alcoholates. The following
formulae show the principles involved in the formation of veronal,
and the basis for its chemical name:

.NH2 .NH2 .OC2H5

C0<( C0<^ C0<^ +NH3^

^NH2 ^OC2H5 ^OCsHb

Urea Urethane ethyl

carbonate >NH2

C0<' +C2HBOH


urethane alcohol
or ethyl

CH20 + >C<; + \c = O ^


Malonic acid Diethyl malonic acid urea


^c<( Vjo + 2H2O

C2H5 ^CONH''^
Veronal diethyl malonyl urea


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Chemical Tests

1. Prolonged boiling with sodium carbonate liberates NH3.

2. In a solution acidulated with HNOa Millon's reagent pro-
duces a precipitate soluble in excess of the reagent.

3. The melting point of the crystals is 187°-188°C.

4. The presence of N is shown by fusing with KOH or NaOH
and making the Prussian blue test, p. 8.

0. .OH

Sulphuric acid may be written /S<^ . The replaceable

hydrogen is not directly attached to the sulphur. When salts
are formed, the replacing metal or radical is also not directly at-

O .0— R

tached to the S, but to the oxygen : \ S<^

O^ ^0— R



(combined or etheral
sulphates), the radical is not attached directly to the sulphur
atom. These bodies are inert and phenyl sulphuric acid occurs
normally inthe urine up to 0.6 grams per day.

Sulphonic acids are compounds in which the carbon of the
organic radical present is in direct union with the sulphur; the
relation between ethyl sulphuric acid and ethyl sulphonic acid
is shown by the formulae :

X X or ><

HO^ ^O HO^ ^O CH3CH, ^
ethyl sul- ethyl sulphonic acid

phuric acid
Where both OH groups of the sulphuric acid are replaced by

radicals, the product is a sulphone:


Digitized by VjOOQ IC


The replaced radical may be methyl, ethyl, or any other alkyl


When acetone is mixed with merci^tan in the presence of
HCl they condense:

CHsv • CH3V yS C2H6

VlO + H.SC2H8 = ^C<^ + HjO

CH3 CH3 S — C2H6

Acetone ethyl acetone-ethyl mercaptol

mercaptan •

This can be oxidized by KMn04 to a sulphone:
CHsv ySC2H5 CHsv yS02C2H6

CH3 DC2H6 CH3 S02C2H6

This is acetone diethyl sulphone or sulphone methane or
diethyl sulphone dimethyl methane: The name is shown by the
following steps:

1. H H

C (methane)



2. CHa.

yC = O (acetone or dimethyl oxymethane)

3. CHsv ySC2H6

(acetone ethyl mercaptol or dimethyl

CHs'^ ^C2H5 diethyl mercaptol methane)

4. CH3. .SO2C2H5

I3 0C2H5

ISv yS02C2xJU{,

yC<(^ (dimethyl methane diethyl sul-

[3 0O2C2H6 phone or sulphonal).


This differs from sulphonal in that one of the CHs groups is
replaced by ethyl C2H5:

CH3 V y.S02C2H5

yC^ consequently * it is diethyl sulphone

C2H5 00202x15

ethyl, methyl methane. It melts at 76°.


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This has all the replaceable hydrogen occupied by ethyl groups:

^ '^r< ^ ^ ^ ^^^ ^ diethyl sulphone diethyl meth-
X N. ane

C2I15 0O2C2H5

Since the pharmacological action of hydrocarbon radicals
increases with the size of the molecule, we should expect trional
to be more active than sulphonal. While this seems to be true
for dogs, it does not seem to hold good for hiunan beings. It
should be emphasized that CH3, or the first of the series, is
nearly always an exception to the rule, both chemically and

Sulphones are not true esters, but bodies of remarkable sta-
bility. They cannot be reduced to sulphides by nascent hydro-
gen. However, their stability outside the body is no criterion
of their pharmacological activity; since some of those that are
most stable are physiologically reactive and more or less de-
composed in the body, while some less stable outside the body
pass through it unchanged and are inert pharmacologically.

Ethylene diethyl sulphone:

CH2.SO2C2H5 J iv 1 ^02C2H6 .,

I and methylene p^j / are easily

OH SO C H ^"^*^yl sulphone ^qq r» tt decomposed

by alcohoUc potash, but may be found unaltered in the urine, and
are only sUghtly active physiologically, whereas, sulphonal,
trional and tetronal, which are unacted on by alcoholic potash,
acids, and many oxidizing and reducing agents, are decomposed
in the body to some extent at least and are actively hypnotic.

Cheinical Tests

Test soliibility of each in water, alcohol, and ether.

Heat 0.1 gm. of each separately with an equal amount of char-
coal in a dry test tube. Each one will be reduced to the sulphur
alcohol which is recognized by its odor, which is similar to

Heat another portion of fusion in a test tube alone, SO2 is
given off and will bleach starch iodide, or methylene blue


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Aldehydes are the first oxidation products of primary alcohols.
Primary alcohols contain the group R, CHjOH. Aldehydes

contain the group RC^ . Where R may be H, CH», CiEt,

or any member of the marsh gas series. In the case of phenol
groups with an aldehyde side chain, almost any complex may take
the place of (R).
Aldehydes may be prepared:

1. By the Oxidation of any primary alcohol;

CH3CH2OH + O = CHr-C/ + H2O


2. CeHjCHjOH + O = C,H^C<f + H2O

benzyl alcohol benzaldehyde

3. By dry distillation of a calcium salt, with calcium formate:
Ca(CHaCOO)j + Ca(H.COO), = 2CH3CHO + 2CaC0, or

(C^6C00)Ca + Ca(HC00)2 = CJltCOH + 2CaC0,

The mechanism of the reaction may be represented;


Any other method of oxidizing an alcohol or reducing an or-
ganic acid may yield an aldehyde.

General Properties of Aldehydes. Reactions.— The char-

acteristic reactions are due to the group — R — C^ which shows

exceptional chemical reactivity: the H atom in combination

with — C^ can be readily oxidized, by the action of oxidizing



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reagents. Since they are readily oxidized, aldehydes act as
reducing agents; and when they are added to an ammoniacal
solution in a test tube of silver nitrate the silver is precipitated
as a silver mirror. For the same reason, they reduce Fehling's

They form addition products readily. This is due to the
C = O group which opens up in the form: C — and the free

' ' \ \

valences add anything in the form of H and X as follows:

.0 .OH

^H ^H

(a) For this reason, they are easily reduced by nascent hydro-
gen the same primary alcohol from which they were derived
being formed —

Jd .OH

CH3C/ + H2->CH8C^H
^H ^H

(6) When shaken with a saturated solution of sodium acid
sulphite, a crystalUne addition product is formed.


CH3C<f + NaHSOs-^CHs— G^OH

^H ^SOaNa

On heating this product with acid aldehyde is again liberated,
(c) Aldehydes unite with ammonia to form aldehyde ammonia


Similarily with hydroxyl amine, NH2OH, hydrazines, etc.,
addition products are formed, the added product always breaking
or ionizing into H and X. The H adds to the O of the
aldehyde, and the X to the carbon.



.,(/ + NH, =

= CH,— G— 0-H



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Caustic alkalies differ from ammonia in their action on
aldehydes. Instead of forming a definite compoimd they
convert the lower aldehydes into resinous bodies of unknown


Formaldehyde H — C\ (Methanal) is the aldehyde of

methyl alcohol CHaOH + = CHOH + H2O. At ordinary
temperatures it is a gas and liquefies at (minus) — 21**C. It
may be prepared easily by heating a copper spiral and dropping
it into methyl alcohol in a test tube. It may also be formed in
the body from methyl alcohol. It can also be derived from hydro-
gen and carbon monoxide under the influence of an electric cur-
rent. At 600°C. it is dissociated into CO and H2. Minute
amounts of it are found in plants where it is highly important, from
a theoretical point of view, in the formation of carbohydrates.
The steps involved may be represented by the following reactions :

1. C02±^C0 +

2. H20->H + OH

3. CO + H2->CH20

4. 6(CH20)->C»Hi206

or carbon dioxide and water may react:

CO2 + H2O =CH20+02

In combination with anmionia it forms hexamethylenamine or
urotropine. When it is evaporated on a water bath, it polymerizes
to form paraformaldehyde (CH2O) 2. Trioxy methylene (CH2O) 3
is a white crystalline compound that separates from formalde-
hyde on standing. It liberates formaldehyde again when it is

Formaldehyde unites with amines, anmionia, sugars, dextrins,
urea, tannic acid, proteins, and many other substances. It
is therefore, a strong antiseptic, a local irritant and a general
protoplasm poison, yet it is surprising how much of it may be
injected intravenously into an animal without killing it. The
reason being that it is oxidized or polymerized rapidly in the body.
Even though it does not kill, it may produce a severe nephritis.
The irritation is probably produced by the union with an amine
group of the proteins.


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The amine and aldehyde groupings may exist in the living pro-
toplasm simultaneously. Loew explained the difference between
living and dead protoplasm on a rearrangement of such a grouping.
In the living or labile molecule or biogen he assumed the group-
ing to be:

H .

— C— NH2

-' y^

— C — C€ In the dead or stable form


— C— N— H

=C— C— OH


such a difference of course would be very diflSicult to prove.

Formaldehyde is valuable in medicine chiefly as an antiseptic,
disinfectant, preservative and cauterizing agent. A solution of
37 per cent, by weight is known commercially as formalin.

On account of its relative physiological inertness and great
antiseptic powers, in vitro, it was thought that formaldehyde
might be injected into, the veins with benefit in cases of tuber-
culosis and other infections. It is now known, however, that it
is rather inert in the body because it is rapidly oxidized, and for
this same reason it possesses relatively little antiseptic action
in the body. In addition it shows no specificity. When the
concentration in the body is sufficient to exert an antiseptic ac-
tion, it will injure the tissues of the body just as readily as the
bacterfa within the tissues. Compounds of formaldehyde like
hexamethylentetramine, that are decomposed in the body and
excreted in the urine, are valuable in cases of infection of
the genito-urinary tract and bladder. The concentration of
the aldehyde in the urine is much greater than, it is in the


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Tests for Formaldehyde

In solutions which are not clear, or in food products which are
to be tested for its presence it is necessary in many cases to distil
and test the distillate from 100 to 200 grams of the substance
which has been acidified with phosphoric acid. Phosphoric acid
is used because it is a non-volatile acid and will not appear in the

1. Add to the formalin solution, diluted if necessary, about 1 cc.
of pure milk or a solution of peptone. Add 1-2 drops of 1 per-
cent, ferric-chloride solution. Carefully pour this solution into
a test tube containing about 10 cc. of strong H2SO4. See that
the two solutions do not mix. At the point of contact a violet
or blue ring will appear. If the solution containing the
formaldehyde is too strong, the result will not be so clear. If
the milk contains less than 1:10,000 formaldehyde, the color,
may not appear for some time.

2. To the milk or peptone solution containing the formalin add
double the volume of strong HCl containing 1 cc. of 10 per cent.
Fe2Cl6 in each 600 cc. of acid. Heat to 80° to 90°C. in a white
dish giving it a rotary motion to cause mixing. A violet color in-
dicates formaldehyde. To test a suspected milk for formalin,
use this same procedure. If the milk has stood for a long time,
it may be necessary to distil it, as a firm combination of the
formalin with the protein prevents the test to some extent.

3. Lieberman's Test. — Mix some of the watery solution of
formalin with a drop of 1 per cent, phenol and pour cautiously,
on some concentrated H2SO4 in a test tube. A crimson zone at
point of contact indicates formaldehyde.

The Cannizzaro Reaction, — In the body, if formalin be given
intravenously, there is both oxidation and reduction of it with
the formation of methyl alcohol and formic acid:

2ncf + H3O = CH3OH + HCOOH

The presence of HCOOH may be shown by collecting the urine,
reducing it with hydrogen and testing for formalin.

4. Rimini's Method. — To 15 cc. of the solution to be tested
add 1 cc. of a dilute solution of phenyl hydrazine hydrochloride,

Digitized by



then a few drops of 1 per cent, ferric chloride solution and finally-
concentrated HCl. A rose red color is given by formaldehyde.
Milk can be tested without distillation by this method, but the
test is more delicate if a distillate is used. Acetic aldehyde or
benzaldehyde do not interfere with the test.

5. Phloroglucinol Test (Jorissen).

Take phloroglucinol 0.1 gram
NaOH 2.0 gram

Aq. q.s. 10.0 cc. Make solution

To 10 cc. of milk or other fluid to be examined, add 2 cc. of this
reagent by means of a pipette, placing the end of the pipette at
the bottom of the tube in such a manner that the reagent will
form a separate layer. A bright red color, not purple, is formed
at the zone of contact, if formaldehyde be present. Some other
aldehydes, give a yellow color. The red color forms quickly and
soon fades.

6. Pheoylhydrazin HCl Method. — Mix 5 cc. of the solution
to be tested with 0.03 gram of phenylhydrazine hydrochloride and
4 to 5 drops of a 1 per cent, solution of ferric chloride. Keep the
test tube containing this in cold water and add slowly with con-
stant shaking to prevent heating, 1 to 2 cc. of concentrated
H2SO4. A precipitate is formed which can be redissolved by the
addition of either alcohol or H2SO4; giving a red color. The
alcohol extract of anything to be tested will also give the
reaction. This test has been found to give reliable reactions in
a dilution of 1 to 150,000 formaldehyde. Acetic aldehyde or
benzaldehyde, does not interfere.

7. Phenylhydrazine Hydrochloride and Ferrocyanic Method.
This method can be applied directly to aqueous solutions or
aqueous alcoholic extracts. To from 3 to 5 cc. add the size of a
pea of phenylhydrazin hydrochloride and 2 to 4 drops (not more)
of a 5 per cent, to 10 per cent, solution of potassium ferrocyanide
and from 8 to 12 drops of 12 per cent. NaOH. A distinct green
or bluish green reaction is obtained in a dilution of 1-80,000

Acetic and benzaldehyde give a color from red to brown and
mask the formaldehyde reaction. It is characteristic only when


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a clear green color is obtained. The method is not apphcable
where blood coloring matter is present, but can be used with milk


Formaldehyde reacts with ammonia to form hexamethylen-
amine.. The reaction is 6CH2O + 4NH8 = (CH2)6Ni + 6HaO.
This is represented as —


1. CH.


CH2 -


/ \

/ \





N— CH2









• \CH2

It is a feebly basic crystalline solid, which dissolves readily in

Hexamethylenamine is a valuable remedy in some cases of
cystitis and infections of the urinary tract. It has also been
used in laryngitis, pharyngitis, poliomyelitis, etc. It has but a
slight irritating action, and only when taken in excessive amounts,
does it cause nephritis or other untoward symptom. It is
found on the market under a variety of names such as urotropin,
cystogen, cystamine, hexamine, etc.

It has some solvent action on uric acid, and has been recom-
mended in gout; but the concentrations that dissolve uric acid
never obtain in the organism. It forms a number of additive
products which have been introduced into medicine, such as
amphotropin which is a combination with camphor; cystopurin,
with sodium acetate; formurol with sodium citrate; cystazol,


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with sodium benzoate. New urotropin, or helmitol, is anhydro-
methylene citric acid: *




None of these compounds have any advantage over hexamethylen-

1. Mix 0.1 gram each of hexamethylenamine and salicylic
acid. Add 6 cc. H2SO4 and heat moderately. A carmine-red
color is produced.

2. An aqueous solution heated with dilute H2SO4 liberates
formaldehyde. If the acid solution is made alkaline with NaOH
and heated gently, NH3 is given oflF.

3. Test the reaction of urine. Take 5 grains of hexamethyl-
enamine. In 30-60 minutes collect the urine. Note the reaction.
Acidify and distil 10-20 cc. Test the distillate for formaldehyde.
It may not be necessary to distil the urine before testing. Make
the test before distillation and, if in doubt, distil and test.


CH3 — C^" is not used in medicine, but some of its derivatives
paraldehyde, chloral and chloral hydrate are important. From a
purely chemical point of view, acetaldehyde is perhaps the most
important aldehyde. It is a colorless liquid, B. P. 21**, sp. gr. 0.8,
soluble in water, alcohol, and ether, dissolves phosphorus, sulphur,
iodine. It occurs as a by-product in all sugar fermentations.
The following method of preparation illustrates strikingly some
of the characteristic reactions of aldehydes: (after Remsen) :

Place 120 grams of granulated potassium bichromate in a 1 to
2 liter flask A.

(a) Place a stopper with two holes in the flask, and set on
water bath.

(6) Insert a funnel tube in one opening and a condenser in
the other. Elevate the condenser at an angle of 45°, so that it


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acts as a reflux. Connect the free end of the condenser by means
of rubber and a glass tube {E) with cylinders F andCr, half-filled
with ether. The glass tubes E and / should dip well into the ether.

Make a mixture of 100 cc. concentrated H2SO4 water 400 cc.
and alcohol 120 cc. Cool the mixture to room temperature and
pour it slowly into the flask.

If the liquid is added too rapidly to the bichromate mixture,
the action may be too violent. Some alcohol may enter the
condenser and flow back again into the flask. The aldehyde is
soluble in the ether. Supply the condenser with wat^r at about

Fio. 1.


30°C. Heat is applied to finish the distillation. After
reaction is ended, the connections are broken and dry NHs
is passed through the cold ethereal solution of the aldehyde.

Crystals of aldehyde ammonia are deposited. The ether and
the crystals are poured on a filter and the crystals washed with
ether. The pure crystals are then placed in a flask and sulphuric
acid added when aldehyde is Uberated. It may be distilled
and condensed in a vessel surrounded by ice.

The reactions involved in the preparation of acetaldehyde are:


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If one inhales fumes of acetaldehyde there is a feeling of suffoca-
tion with coughing. In animals its irritative action causes excite-
ment followed by depression, and paralysis of respiration. A
considerable portion of ingested aldehyde is oxidized in the body,
traces escape in the breath and more in the urine. Kunkel
describes a condition of aldehydeismus in people exposed to alde-
hyde fumes. In such cases there is thickening of the adventitia
of the vessels and an increase of connective tissue between the
lobes of the liver.


(CH3CHO)3. This is the polymer of acetaldehyde. It is
detected only after being reconverted into acetaldehyde.

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