SYNTHETIC AND SPECTROMETRIC STUDIES OF SOMEPYRAZOLONESl

By Paur E. GacNoN, JnaN L. BorvrN2, aNt R. NonuaN JoNns

Abstract

i::il, :$#:*nLd T"-d T;,H "::from chemical reactions and ultra-violet absorption spectra determinations. A rnixture of two tautomeric forms

IntroductionThe first investigations of 3-amino-5-p1'razolones (I) were carried out in

1906 by Conrad and Zart (2), who treated ethyl cyanoacetate with phenyl-hydrazine and obtained a product which the-v assumed to be 1-phenyl-3-hydroxy-5-pyrazolone. The compound proved to be of some importanccin color photography (7). In 1941, Weissberger and Porter (9) prepared1-phenyl-3-amino-5-pyrazolone from ethyl oxalacetate and phenylhydrazineand showed that the compound of Conrad and Zartwas the same. In 1937,other 3-amino-5-pyrazolones were prepared by Hepner and Fajersztejn (a).

R2

c_c_NH,,/l' ,l

RrlllC5 2N

/ \"/ONRr

I

Rr, R2 : H, alkyl, or aryl group

Ra: HorCoHr

In 1947, Gagnon, Savard, Gaudry, and Richardson (3) observed that crudealkyl-cyanoacethydrazides, on standing for some time, underwent transforma-tion to the corresponding 4-alkyl-3-amino-S-pyrazolones. These authors pre-pared for the first time 3-amino-5-pyrazolones substituted only in position 4.

L Manuscripl receiaeiJ January 3, 1919.Contri.bulion Jr.om the Department of Chemistry, Laual Unioersily, Quebec, and. the Diaision

of Chemistry, NaLioial Researcir. Laboratories, Oltawa, Canaila. Isiued, os N.R.C. No. 1903.This paper constilutes part oJ a thesis subrnitled. to lhe Grod.uate School, Laual Uniaers,ity, in partialfulfl[nint oJ the requiTemeitt 7or the ilegree oJ Doctor oJ Science.

' of a Showinigan Chemicals Limited' ResearchSchola irch Counc,if, of Canada. Present aildress:L)anad blishment, valcartier, euebec.

Can

. J. R

es. D

ownl

oade

d fr

om w

ww

.nrc

rese

arch

pres

s.co

m b

y U

nive

rsity

of

Tor

onto

on

09/0

6/13

For

pers

onal

use

onl

y.

GAGNON ET AL': STUDIES oF SOME PYRAZOLONES 191

Pyrazolones substituted in positions 1 and 2 had already becn reported

2300 2500 270

wAvELEnutt titFrc l' ',lv

iTii::nryroll,li"Tfl,), a,,",,t

transformed to one of them completely by acid catalysis'

B. |-Monosu enyl-3-amino-5-pyrazolozes.-These pyrazolones were

prepared by n of the method of Conrad and Zart (2) ' The ferric

chloride test e; the compounds were soluble in strong alkalies.

c.4,4-Disubstituted,-3-amino-5-pyrazolones.--The pyrazolones were prepared by

the method described for the 4-monosubstituted-3-amino-5-pyrazolones' A

concentration higher than one equivalent of alkali per mole of pyrazolone

precipitated the alkali salt.

Can

. J. R

es. D

ownl

oade

d fr

om w

ww

.nrc

rese

arch

pres

s.co

m b

y U

nive

rsity

of

Tor

onto

on

09/0

6/13

For

pers

onal

use

onl

y.

192 :ANADIAN J\rRNAL oF RESEARCH. voL. 27. sEc. a.

ExperimentaltThe properties of the pyrazolones are summarized in Tables I and II. The

yields ranged from 75 to gsTo. The melting points are uncorrected.

TABLE IGnxpner, pRopERTIES oF pyRAzoLoNES

CompoundReactions

4-Monosubstituted-3-amino-5-pyrazolones4-Monosubstituted-2-phenyl-3-amino-5-pyrazolones4,4-Disubstituted-3-amino-5-pyruolones4,4-Disubstituted-2 -phenyl-3-imino-5-pyrazolones

s : soluble, i : insoluble, s.s. : slightl! soluble,

in luble in water, insoluble

ins h a hyilroryl group a.repage 2 1).

the pyrozolone precipitateil

4 - M ono s ub s titut ed, - 3 - amin o - 5 - py r azol o n e s

These compounds were prepared by the following methods:(a) crude monosubstituted cyanoacethydrazides (0. 1 mole) were treated

with sodium hydroxide (4070,0.2 mole). The reaction was exothermic.The solutions were allowed to stand at room temperature for two hours andwere neutralized with acetic acid (s0%). The precipitates were filtered off,washed with ether to remove any substituted malonic acids formed in thereaction, and recrystallized several times from water or ethanol.

(D) To a solution of sodium ethoxide (0.2 mole of sodium and g0 ml. ofabsolute ethanol) was added a mixture of ethyl substituted cyanoacetates(0.1 mole) and hydrazine hydrate (r00To,0.1 mole). The solution wasrefluxed for half an hour on the water bath. The solvent was removed underreduced pressure, the residue dissolved in water (100 ml.), and the solutionextracted with ether (50 ml.) to remove unchanged esters. The aqueous layerwas neutralized with acetic acid and allowed to stand in a cold place, where asolid crystallized out.

-,-.^-,1,7!,.*d!rod.s.of .prep^aration ol the coryp.ouTils used to slm.thesize the iliferenr pyrazohnes aregllten tn o Prdrows Papet (Gagnon, P. E. anil Boivin, J, L. eon. J. Research, n, za i sos. to+a.1.

Pos.Pos,Pos.Neg,

Pos.Neg.Pos.Neg.

WaterlAcids lAlkalies

Can

. J. R

es. D

ownl

oade

d fr

om w

ww

.nrc

rese

arch

pres

s.co

m b

y U

nive

rsity

of

Tor

onto

on

09/0

6/13

For

pers

onal

use

onl

y.

GAGNON ET AL.: STUDIES OF SOME PYRAZOLONES

TABLE II

Pnopotrrps oF INDTvTDUAL PYRAZoLoNES

Analysis,%

Formula M.p.,'C' Nilrogen Neutral

193

Ultraviolet absorPtionmaxrma

Compound

4-Mooosubstituted-3-amino-5-pyrazolones

4-Methyl

4-Ethyl

4-(2-Phenoxyethyl) -

4(3-PhenoxyproPYl) -

4-Phen1-l

4-Benzyl

4-Monosubstituled-2-PhenYl-3-amino-5-pyrazolones

4-lUelhyl

4-Ethyl

4-(2-Phenoxyethyl) -

4-(3-PhenoxYProPYl) -

4-Benzyl

pyrzolones4,4-Dibenzyl

4,4-(2,2-spiro-IndanYl) -

4,4-Disubstituted-2-phenYl-3-imino-5-pyrazolones

4,4-Dibenzyl

Acid

Calc. I Found

CrHzONs

CoHrONr

CnHuOzNr

CrzHroOrNr

CcHgONr

CroHrrONr

CroHnONr

CrrILrONr

CrrHrsO2Nr

CrsHrsGNs

CroHrrONs

CrrHrrONr

CnHrrONr

CzrHrrONr

246-247

203-20+

227-228

213-214

136-137

108-109

160-161

242-2+3

238 239

259-260

242-243

247-2+8

186-187

+1.7

32.5

18.7

2700

2840

278027tO2430

27aO270,0

2+60

2560

2470

2500

2500

2560

2530

2520

2760

27+O2670

3.61

3 .56

3.263 .344.05

3.423 .464.06

4 -21

4.08

4.22

4.23

4.26

4,22

4. 15

2600

2700

276027fr)2380

278027002360

2460

2360

2660

2680

27o0

270,0

2700

2660

27302660

3.68

3 .50

3.093.2r4.O7

3.073.174.05

4. 19

4.05

+.23

4. 1t

4.25

4. 16

4.21,

3 .60

3.7+3 .76

J.)v

18. O

2+.O

22.2

22.2

20.7

t+.2

13 .6

15.9

14. O

20.9

23.8

22.O

22.l

20.4

14.2

13.4

15 .3

l5.o

20 .8

J.)/

3.733 .70

3.55

test was posltlve.

4-Ethyl,-3-arnino-5-pyrazolone.-Ethyl-a-cyanobutyrate (14' 1gm'' 0' 1mole)

was stirred rvith hydrazine hydrate (100Ta,5'0 gm',0'1 mole)' The solution

Can

. J. R

es. D

ownl

oade

d fr

om w

ww

.nrc

rese

arch

pres

s.co

m b

y U

nive

rsity

of

Tor

onto

on

09/0

6/13

For

pers

onal

use

onl

y.

194 :ANADTAN JIzRNAL oF RESEARCH. voL. zz, sEc. a.

was allowed to stand at room temperature, whereupon solidification took place.The white solid was treated with two equivalents of sodium hydroxide. Thereaction was exothermic. The resulting solution was allowed to stand atroom temperature for two hours, when crystals appeared. The mixture wasneutralized with dilute acetic acid and evaporated to dryness on the waterbath. The material was extracted with ethyl acetate in a Soxhlet during12 hr. The solvent was removed under reduced pressure and the residuerecrystallized several times from ethanol. The ferric chloride test was positive.

tautomer into another, which was not affected by further treatment withsodium hydroxide. The material (5 204" C.,was then refluxed for half an hour in c acid inwater. The reaction mixture was reducedpressure. The residue was dissolved in a normal solution of sodium hydroxidein water and the resulting solution was neutralized with dilute acetic acid.A solid se g in a cold place. It was filtered out, washedwith ethe om a fairly large volume of water: m.p. 203oto 204" C The ferric chloride test was positive.4-Monosubstitured-2-phenyl,-3-amino-5-pyrazolones.-To a solution of sodium

solidified. It was washed with dilute sodium carbonate to remove any sub-stituted malonic acids formed in the reaction, and recrystallized from ethanol.

pressure. The residue was dissolved in hot water (100 ml.). on cooling, thesodium salt of the pyrazolone cr\'stallized out. It was separated by filtr;tion,washed with ether and finally with dilute hydrochlori.

".id. The filtrate wasextracted with ether to remove unchanged ester. The aqueous layer wasneutralized with acetic acid and allowed to stand in a cold place. The crystalsformed were combined with the solid material previously oitained. The solid

Can

. J. R

es. D

ownl

oade

d fr

om w

ww

.nrc

rese

arch

pres

s.co

m b

y U

nive

rsity

of

Tor

onto

on

09/0

6/13

For

pers

onal

use

onl

y.

G/GNOI ET AL.: STUDIES OF SOME PYRAZOLONES 195

mixture was washecl u'ith ether, to removc any disubstituted malonic acids

forrned in the reaction, and rccrtstailized several times from a large volume

of water.

4,!-Disubstituted o-5 -PYYaz were

prepared by the above fo no-S-

pyrazolones, but was used time

of heating in an oil bathlvas 18 hr.

Ultraviolet AbsorPtion SPectra

The ultraviolet absorption spectra were determined on a Beckman spectro-

photometer; the experimental details have been reported previously (3). The

data are plotted in Figs. 2-9. The spcctra may be divided into two distinctgroups' designatcd the "high intensit]"' and the "low intensity" tl'pe' in

Table III.

4.O 4.O

t 3.6

C'

oJ

3.?

Elrl

5.6('oJ

3.2

2.5 ?.e

2400 2800

WAVELENGTH (A)Fic. 2.

24AA 2800o

w avE L ere rn (A)Ftc. 3.

Frc. 2. L'llrauiolet absorplion spe(ltd.

-

1- M ethyt- 3 -a m i.i o- 5 - p y ra z ol o ne (,e I h a n ol)- ' ,r ,, (N hyd.io in 90/6 ethanbl)..'' " 4-Methyl-Z-phcnyl-3-amino-5-pyra:olone-'<- '- -' - '' 't ('rr c acid' i'n 907o ethanol)'

Frc. 3. Ultroviolet absorption speclra.

-

4-Ethyl-3-amino-5-pyrazolone ochroricacid,'in90/6erhanot).

."" 4-Elhyt-2-phenyl-3-amino'5-p (ethanol)' --,. '"4"'" - ,i "'- - ' '(Nhydiochloricaciiling0a/6ethanol),

\..\ "..

r \r\\\\\\\Itrrl\rf\\1:\

II

\\l\t\r

\rII

Can

. J. R

es. D

ownl

oade

d fr

om w

ww

.nrc

rese

arch

pres

s.co

m b

y U

nive

rsity

of

Tor

onto

on

09/0

6/13

For

pers

onal

use

onl

y.

196 CANADIAN JOURNAL OF RESEARCH. VOL.27, SEC. B.

TABLE IIICr,essrnrcerroN oF ULTRAvToLET ABsoRprroN spEcrRA

Acid shift on principalmaxlmum

Compound

Hypsochromic

Bathochromic

(-110 A)(-so )(-1oo )(-100 )(+160)(+180)(+180)(+140)(+170)

XXXXXXXXXXIxxIXXIxxIxxI

B. Low intensity type spectra

4-Methyl-4-Ethyl-4.4-Dibenzvl-4,4- (2,2 -spir o-Indanyl) -4,4-D ibenzyl-2-phenyl-

Hypsochromic

aa

( - 100)( - 140)( - 100)(- 10)(Nil)

XXIII (or XXII)XXIII (or XXII)XXIII (or XXII)XXIII (or XXII)XXII

4.0

3.6

2.e

'*.\

\\.\\

'I

\',IIIIIt

2 6()0 3O0O

wAvELEilcrH (i)Frc. 4.

4.0

gtl

c,oJ

U3.€

C'o)

3.2

2600 3000o

WAVE LE NG T H (A)Frc. 5.

Ftc, 4. Ultraaiolel absorption spectra.

-

zl,4- D ib enzyl- 3 - a m i n o - 5 - py r a zol on e (ethanol)." (N hyd.rochl,oric acid in 90/6 ethanot).

. . .' . 4,4-D ibenzyl- 2 - phen yl-3-i m in o-5 -pyiaz.ol,one (ethanot)" " '. (N hyilrochloric acid, in 90/s ethanol).

Ftc. 5. Ul.lraviole!, abso

-

4,4-(2,2- )-3-amino-5-pyrazolone (ethanot)." '3 ..- - (N hydrochloric acid in 90/ ethanol.).

A. High intensity type spectra

\\

Can

. J. R

es. D

ownl

oade

d fr

om w

ww

.nrc

rese

arch

pres

s.co

m b

y U

nive

rsity

of

Tor

onto

on

09/0

6/13

For

pers

onal

use

onl

y.

GAGNON ET AL; STUDIES OF SOME PVRA^OLONES 197

The spectra of the 4-monosubstituted-3-amino-5-pyrazotoncs are not all

similar. The simple 4-meth1'l and 4-ethyl derivatives (Figs' 2, 3) possess.a

broad band of relatively low intensity rvith a maximum at 2700 to 2900 A'

The position of the maximum is shifted hypsochromically in acid medium'

The spectrum of 4,4-dibenzyl-3-amino-5-pyrazolone is similar (Fig. a).

€lr,

(9

oJ

4.O

3.6

2.4

FU

Io

2600 3000o

WAVELENGTH ( A)

l:re. 6.

a 600 3ooo

wAvELenorn (i;Frc. 7.

Frc' 6' yyy hne (ethonol), bcJorc refluxing with aciit'

Frc. 7. -ut*)iotr,

absorption spectra. cid in 9070 ethanol)'

----- 4-Benztlj|-pheiyt-3-amino-S-pyra,zolone wiil;r* acid, in 90/s ethanol).

The curve of the 4-monobenzl'l derivative differs considerably from those

considerably shorter wave-lengths. This indicates a difference in the ring

chromophore, since the phenyl group in the side chain cannot be in conjugation

with the ring, and its additive contribution to the total absorption of the

molecule would be negligible (5).

I

I

III

Can

. J. R

es. D

ownl

oade

d fr

om w

ww

.nrc

rese

arch

pres

s.co

m b

y U

nive

rsity

of

Tor

onto

on

09/0

6/13

For

pers

onal

use

onl

y.

198 C.4NADIAN JIIRNAL oF RESEARCH. voL. zz, sEC. B.

In the spectra of the 4-(2-phenoxyethyl)- and 4-(3-phenoxypropyl)- deriva-tives (Figs. 8 and 9) the additive contribution of the side chain chromophoresto the total absorption is quite large. In Fig. 10 the curve obtained by sub-

E

ut

c)o

4.O

3.6

3,2

2.8

't..zl

\

\\

\ -,.l-rI

I

I

I

2600 3000WAVELENGTH tiT

Frc. 8. Ultraaiolet absorption spectra.

- 4- (2 - P henoxyetkyl,) - 3 - amino- 5 -pyr azol.one(1/ ric acid in 90/6 ethanol.).

. ... ... 4_(2_phenoxyethyt)_2_phenyt-3_amino_rri roo,""r,"|l*;k e0To ethanot).

traction of the spectrum of phenetol from that of 4-(2-phenoxyethyl)-3-amino-S-pyrazolone is compared with the spectrum of the 4-benzyl compound. Theevident similarity shows that in the 4-phenoxyalkyl derivatives the ringstructure is similar to that of the 4-benzyl compound and different from thatof the 4-methyl compound.

The spectrum of 4-phenyl-3-amino-5-pyrazolone (Fig. 11) is also simirarin general type to that of the 4-benzyl compound but it is shifted by some

Can

. J. R

es. D

ownl

oade

d fr

om w

ww

.nrc

rese

arch

pres

s.co

m b

y U

nive

rsity

of

Tor

onto

on

09/0

6/13

For

pers

onal

use

onl

y.

GAGNON ET AL': STUDIES Ob SOME PYRAZOLONES 199

100 A to longer $,ave lengths. This u'ould be in accord u'ith a basic ring

system similar to that of the 4-benzyl derivative; the bathochromic shift

resulting from the extra conjugation of a phenl'l group attached directly to

4.O

E s.eui

(9,

o-.!

3.2

2.8

2600 000

WAVELENGTH (i}Frc. 9. Ultraaiolel absorption spectra'

4-(3-Pheioxypripvrl-s-ami'no-S-pvra"ix{;ry:::#:k acid. i.n e,/p ethanor).

' ' ' ' ' 4-(3-P henoxypropvl)-Z-phenyl-3-amini-5-iyra'.ol'o'e (ethanol) '.. .. (N hyiiochl'oric acid'in 90/6 ethanol').

the heterocl,clic ring. It is to be noted that in all these 4-monosubstituted

compounds, the spectra are shifted to shorter wave-lengths in acid'

TheSpectraofthe4-monosubstituted.2-phenyl-3-amino-5-pyrazolonesdiffcr from those of the corresponding derivatives which lack the 2-phenyl

group (Figs . 2-.4, 7-.g). The absorption is more intense and on the addition

of acid the curves are displaced, bathochromically or not significantly altered

(Table III).

, '.... .\

\ /'l\/ llt

\\I

II

rlti

uJII

lrt!

lrtt

lrrIr'.t'

Can

. J. R

es. D

ownl

oade

d fr

om w

ww

.nrc

rese

arch

pres

s.co

m b

y U

nive

rsity

of

Tor

onto

on

09/0

6/13

For

pers

onal

use

onl

y.

200 IANADTAN JouRJ,tAL oF RESL,ARCH. voL. zz, sEC. B.

4,4-Dibenzyl-2-phenyl-3-imino-5-py razolone (Fig. a) possesses a specrrumwith a single maximum of lower intensity similar to that of the 4-methyl and4, -dibenzyl derivatives. on acidification the position of the maximum isnot changed.

F5

ooJ

a.o

2,3

4.O

5.6

2.A

2600 3000o

WAVELENGTH (A)Frc. 11.

EU

e,oJ

3.2

aloo 2500 ?700

wAvELercrx 1i1Frc. 10.

Frc. 10. UltraoioA -.-..-B -..-..C _ _ @thanol).

D

-

oJ Curae A from Curue B.Frc. 11. Ultraaiolet absorption spectra.

4- P henyl- 3 _amino_ 5 _pyr azolon e (ethanol)." (. ., (iy' hytlrochloric aciit in 90/6 elhanol).

DiscussionAssuming, on the basis of the elemental analyses and general chemical

behavior, that these compounds alr contain the pyrazolone ring system, thedifferences observed in the absorption spectra must be associatea wiirr differenitautomeric forms.

\

II

II

I

II

\\

Can

. J. R

es. D

ownl

oade

d fr

om w

ww

.nrc

rese

arch

pres

s.co

m b

y U

nive

rsity

of

Tor

onto

on

09/0

6/13

For

pers

onal

use

onl

y.

GACNON ET AL': STUDIES oF SOLIE P(RAZOLONES 201

It is not possible, from the spectra' to distinguish unequivocally among the

several po..ibl" tautomeric forms, but a comparison of the absorption Curves

does reveal that the spectra fall into well defined classes, as shown in Table III.This classification is based on the shape and intensity of the curves and on the

direction of the displacement in acid.

In the following discussion, an attempt is made to relate the spectra with

specific tautomeric forms. The arguments presented are frankly speculative

urrd ult"r.rutive interpretations are probably possible. The chemical evidence

of structure derived from the ferric chloride and nitrous acid tests (Table I)is considered also in relation to the spectrographic data'

The 10 tautomeric structures II-XI represent the basic formulae which may

be considered a priori for 3-amino-5-pyrazolone, and the 4-monosubstituted

derivatives may be written in terms of any of these' In the 4,4-disubstituted

derivatives the choice is restricted to II, III, IV, V, and X' The 4-monosub-

stituted-2-phenyl derivatives may have structures II, IV, VI, VII, or IX'but for the +,4-clisubstituted-2-phenyl-3-imino-5-pyrazolones only II and IVare possible.

HH\_.:N",/l IHl

I1lOC NH

\.,/NH

II

H-C::=C-NH,lltlOC NH

\_6_NH,r/l lltll

OCN\,,/

NH

III

H-C::=C-NH,lliNH,/ \,/HON

H

\_c:NH,/l IHl IllCNH

,'\,/HON

IV

H-C-c-NH,11 ilJl-,/ \,/HON

H

VIII

V

H-C-C:NHIlillCNH

,/ \,/HONH

IX

Displacement oJ Spectra on Acidif'cation

Consideration of the spectra indicates that, in addition to their classification

in terms of intensity, the compounds may be divided into those in which the

absorption maximum is displaced considerably to shorter wave lengths on

NHr

NH

VI VII

H-C--cH-NH,ll,,/ \,/

N

XIHO

Can

. J. R

es. D

ownl

oade

d fr

om w

ww

.nrc

rese

arch

pres

s.co

m b

y U

nive

rsity

of

Tor

onto

on

09/0

6/13

For

pers

onal

use

onl

y.

202 :ANADTAN JzyRNAL oF RESEARCH. voL. zz, sEC. B.

acidification (hypsochromic), and those in which the displacement is batho-chromic or negligible.

Displacement to shorter wave lengths on acidification is very suggestive ofan amino group directly attached to a conjugated system, as in the partialstructures XII and XIII. In the neutral molecule these may resonate withXIIo and XIIIo, but on acidification the possibility of this type of resonance islost in the amine ion. This behavior is seen commonly in the spectra ofaromatic amines (6) and would be expected from pyrazolones having thestructures III, V, VI, VII, VIII, X, and XI.

-+R-C-C:NH,

XIIa

l*R-C-C:NHZll N-,/XIIIa

The type of structure which might give rise to a shift to longer wavelengths on acidification is not so easily recognized. one possibility might bethe imino structure XIV. In the ionic form XV resonance can occur withXVo, the system bearing a formal analogy with that of a carbocyanine dye,the spectrographic properties of which have been examined extensively byBrooker (1). In the neutral molecule, resonance between the analogousstructures XIV and XIVo would be suppressed by the separation of chargeand the instability of the -NH- group. on the basis of this argument onemight expect a shift to longer wave lengths on acidification of pyrazoloneshaving structures II, IV, IX.

-<---->R

XIV

l*_C-C:NHZ

N

R

XV XVa

Signif,cance of Ferric Chlorid,e and, Nitrous Ac,id, ReactionsThe development of color on addition of ferric chloride in acid solution is

generally regarded as indicative of a phenolic hydroxyl group (8), either presentin the molecule as such or.readily derived as a result of an equilibrium

R-C:C-NH2 <->

XII

I

R-C-C-NH:I ll <---->

N

XIII

-<_--->

I

CI-C:NH

I

N

t--C-C-NHlil

N+

R

XIVa

I

-cI

Can

. J. R

es. D

ownl

oade

d fr

om w

ww

.nrc

rese

arch

pres

s.co

m b

y U

nive

rsity

of

Tor

onto

on

09/0

6/13

For

pers

onal

use

onl

y.

displacement.are indicatedon additionpotential free

GAGNON ET AL.: SI'UDIES OF SOME PYRAZOLONES 203

In the 3-amino-S-p1'razolones the partial structures XVI-XIXby a positive response to this test. Thc liberation of nitrogen

of nitrous acids identifies a structure possessing an actual or

primary amino group"

H-C_Ic

/\o

XVI

-c-ti

C

HO

X\-II

-c-I

L/\,/O,N

H

XVIII

-c-I

C//\//HON

xIx

R-C::C-NH,

"i i,-NHu

CoHt

NH

Structure of Compound,s with High Intensity Spectra

give a positive and the 4-monosubstituted-2-phenyl derivatives a negative

ieactio.t, and, of the structures listed above, only type VI will satisfl' 1[i5

criterion. On this evidence structures XX and XXI may be proposed for the

compounds giving the high intensity spectra.

R-C::CtltlOCN\,,

NI

H

XX XXI

This conclusion is consistent with the positive rcaction in the nitrous acid

test, and the solubility behavior (Tablc I). It accounts also for the hypso-

chromic displacement of the spectra of the 4-substituted-3-amino-5 -pyrazo'

lones on acidification.*

It does not account hor'vevcr for the bathochromic displacement of the

spectra of the 2-phenyl derivatives in acid, at least in terms of the mechanism

proposed in Formulae XIV and XV which require an imino group atposition 3.

Cotnpounds Giving Low Intensity Spectra

This group (Table III) includes 4-monosubstituted, 4,4-disubstituted, and

4,4-disuLstituted-2-phenyl-3-imino-5-pyrazolones. If the similarity of the

oJ 4-ohe one conforms closely to thot-of the zl-benTll

der |*ui ii longer waue lengths' .fhil slilt suggests th-at

;i; ii"gitid hore", and is alsi consistent with structure XXfor

Can

. J. R

es. D

ownl

oade

d fr

om w

ww

.nrc

rese

arch

pres

s.co

m b

y U

nive

rsity

of

Tor

onto

on

09/0

6/13

For

pers

onal

use

onl

y.

204 :ANADTAN JIzRNAL oF RESEARCH. voL. 27, sEc. B.

spectrum in acid.In conclusion, it must be emphasized that these assignments of structure

based on evidence from ferric chloride and nitrous acid testi, and from similarity(but not identity) of spectra, can only be considered as tentative. The

R1

c_c:NH,/l IR2 l ItlOC NRS

\,./NH

XXIIRr : Alkyl Rz : H or alkyl

Rr

Rz

N'HXXIII

Re: HorCoHs

References1. Bnoor<rn, L. G. S. Revs. Nlodern phys. 14 :290. 1942.2. CoNneo, M. and Ztrtr, A. Ber.39:22g2. 1906.3. GecNo_r,

^P^. E., S-q.veno, K., Geuonv, R., and Rrcuenoso*, E. D. Can, J, Research, B,25:.28. 1947.

4. Hrrxnn, B, and FlyrnszrnlN, S. Bull. soc. chim. France, 4 : g54. 1937.5. JoNes, R. N. Chem. Revs. 32 :1. 1943.6. Jonrs, R. N. J. Am. Chem. Soc.67 :2127. 1945.7. Kooer Ltd., London. Brit. patent No. 47g,990. January 24, lg3g.8. Rorunweurc, R. J. prakt. Chem. 52 :45. 1g95.9. Werssenncen, A. and Ponrrn, H. D. J. Am. Chem. Soc. 64 :2133. 1912.

10. WBrssnnrcen, A. and Ponrun, H. D. J. Am. Chem. Soc. 65 : 52. 1gL3.11. WBrsseuRcen, A. and Ponren, H. D. J. Am. Chem. Soc. 65 : 732. 1943.12. WorsssBncen, A. and Ponrrn, H. D. J. Am. Chem. Soc. 66 :1g49. 1944.13. Wrrsse'ncrn, A., Ponron, H. D., and Gnnconv, W. A. J. Am. Chem. Soc. 66 :1g5t.

1944.

Can

. J. R

es. D

ownl

oade

d fr

om w

ww

.nrc

rese

arch

pres

s.co

m b

y U

nive

rsity

of

Tor

onto

on

09/0

6/13

For

pers

onal

use

onl

y.