The reactions of diphenylcarbazide and diphenylcarbazone with cations

188

ANALYTICACHIMICAACTA

THE

REACTIONS

OF

DIPHENYLCARBAZIDE

DIPHENYLCARBAZONE PART

II*.

EXTRACTION

BEHAVIOUR S. %%L/1’AND

Chemicul

WITH

Labovalovy,

Fvee

AND E.

VAN

AND

CATIONS

SPECTRA

OF THE

REAGENTS

DALEN (TireNetlrevlands)

Univevsily,Amsterdam

(ReccivcclDcccnlbcr zSth, xgb~)

Although diphenylcarbazide and diphenylcarbazone have been used in analytical chemistry for many years, very little is known about the composition and stability constants of the colored complexes they can form with certain cations ,and about the behaviour ‘of diphenylcarbazone as an acid. CAZENEUVE~ and BAMBERGER*;~ reported that diphenylcarbazone can split off only one proton to form the mono-sodium or -potassium salt, which would prove diphenylcarbazone to be a monobasic acid, while the carbazide did not form the corresponding salt. The sodium salt of diphenylcarbazone is strongly colored; BAMBERGER~ takes this fact to indicate that diphenylcarbazone is present in the enolic form in this compound. From the ultraviolet spectrum GRAMMATICAKIS4 concluded that in alcoholic solution both reagents resemble azo compounds and differ from formazanes, so that in thetautomeric equilibrium between the ketonic(1) and enolic form(I1) of the carbazone, postulated by many authors 6, the first component is in excess:

*.

N--N-&Ha

N-N-C&IO O=C

/

‘+a

\r,

‘--N-C,+1 I-1 H

H

\&_tif I,

(1)

..

c H -

0

0

(11)

In 1937 I
I: Awnl.

Chim.

Acta,

25 (x96x)

507. AlraZ. Chim.

Ada,

27 (1962)

188-195

DIPHENYLCARBAZIDE

AND

DIPHENYLCARBAZONE

COMPLEXES

289

EXPERIMENTAL Commercial

diphenylcarbazone

Diphenylcarbazide The

(pro

solvents,

of analytical

purity.

perchloric refluxing

acid

with

a Unicam

SP

analyse)

analyse)

was

and

a Philips

g4oo

were

was

to KRWMHOLZ~.

alcohol.

and the other

Toluene

with

teflon

pH-meter.

500 spectrophotometer

on the Perkin-Elmer

from

according

chemicals

made

made

by

used

were

all

neutralization

of

methylthiophene-free

by

alloyo.

equipped

PR

purified

solutions

hydroxide.

a sodium-potassium were

water,

perchlorate

sodium

was

recrystallized

tetrachloride Sodium

funnels

measured

in KBr

with

with

Separatory

recorded

carbon

(pro

stoppers

in I cm quartz

Infracord

and

Extinction

for

stopcocks.

measurements cuvettes.

the carbazone

Infrared

itself

and

The were

PH was made

spectra

on

were

the sodium

salt

discs. RESULTS

Solutions (WO

of diphenylcarbazone

-3-10-5

M)

obey

Beer’s

in carbon law.

Fig.

tetrachloricle

I gives

the

(IO+-

spectra

10-6 M) of the

and

in toluene

carbazone.

Table

I

Fig. I. Spectra of diphenylcarbazone and diphcnylformazanc. x0-3 M diphcnylcsrbazone in carbon tetrachloridc. -- - 10-3 M diphcnylcarbazone in tolucne. . . . . 10-3 M diphcnylcarbazonc anion in water, pH = X0.5. -.-•-•IO- a M diphcnylcarbazonc in water, PH = 1.0 (converted). -o-o^o10-a M diphcnylcarbazone in water, pn = 1.0 (converted from a saturated solution, 4-cm cuvcttcs). *-.-.10 --3 M N,N’-diphenylformazanc in toluene.

TABLE ABSORPTION Garbott

288 rnp 465 rnp 555 rnp

(x2.5 f (3-04 f (0,gr f

MAXIMA

AND

MOLAR

EXTINCTION

I COEPPICIENTS

fetrnchloride

0.5). 0.05) o.oG)

x08 cm-1 * 103 cm-1 . I03 cm-l

Ol? DIPHENYLCARBAZONE Tulue,ae

mole-r 1 mole-’

mol&r

1 1

289 m,u 467 mp 565 mp

(10.8 & 0.1). xoa cm --1 mole-1 1 (r .2 I f 0.05) * 103 cm-r mole-r 1 (0.47 * 0.02) - 10a cm-1 mole-1 1 Anal. Chim. Ada,

27 (1962) x88-193

S.BALT,E.VANDALEN

190

gives the wavelengths of maximum absorption for both solvents as well as the molar extinction coefficients. Care was taken to keep the solutions in the dark because irradiation alters the spectrum. With the data given above, the saturation concentrations were measured spectrophotometrically and were found to be 2.75 * IO -3 M in carbon tetrachloride and 1.0 a 10-2 M in toluene. To evaluate the partition quotient for undissociated diphenylcarbazone between water and the two solvents, zzg ml of water was shaken with 15 ml of the organic phase containing the carbazone in varying concentrations. In all extraction experiments the solvents of both phases were mutually saturated beforehand. The extinction was measured before (E) and after (E’) the shaking. Equilibrium was attained after 5 min of shaking. $Ory. = (cliphenylcarbazonc)ors./(diphenylcarX 225115. Table 11 gives #ccl, for bazone)wnlcr was calculated from fi = ~!?l(n-E’) various pH values and compositions of the aqueous phase. The PH was kept low to prevent complex formation with traces of metal ions and acid dissociation of the carbazone. For toluene, the partition coefficient proved to be independent of ionic strength in a perchlorate medium (0.1-1 M). The value 39 )_ z was found.

PARTITION -

PH

OIr

DIP,IISNYLCARBAZONE

BETWRRN

cc1.1

Solut~‘.r iu fho crqueocts fhrse

pco,

only HClO4 only MCI04 HC104 _1- N&104, HC104 + NaC104,

O.L M in lofo 0.1 M in lofo

0.97 I .28

HC104 HC104 HClO4 I-iC10.1 i-ICI04

-I-k -f-t -I_

o. I 0.1 0.1 1.1 I +r

0.8X

I-l&04

0.82

I-IaSO.1

o*79 o-77

I&.SO,I H&04

only only -j- NanSO4, + Na~S04,

o-77 o *95 I .08 1.10 x.x2

1.51 2 *go

NuCIO4, NaClO.~, NaClO.1, N&104, NaC104,

WA’TISR

AND

7.4

M M ICI M

Z:; 7.4

,irz lolo

,irz lolo irt folo

,in lolo M ,irz loto

;:a 8.4 7.9 7.1 10.5 9.5

I .I M ,ita lolo

21.2

I. I M in lolo

19.8

ml of a 10-3 M solution of cliphenylcarbazone in an alcohol-water mixture with 1.3. IO --2 iV barium hydroxide. The curve did not show any steep rise; the only equivalence point occurred at ~1% 9.6, when one equivalent of base was consumed, hence the carbazone behaves as a monobasic acid. Diphenylcarbazide did not consume any base. The sodium diphenylcarbazonate was isolated by partial evaporation of the basic solution prepared by dissolving the carbazone in water at PH 10.5; 10-4 M potassium cyanide wras added to complex traces of metals. After filtration, washing with a little water and drying,, the salt. was treated with sulphuric acid to yield sodium sulphate. Weighing the sulpbate confirmed the sodium diphenylcarbazonate as the monosodium salt. IOO

(20

: 80 v/v) was titrated

Anal.

Claim.

Ada,

27

(1962)

188-193

DIPHENYLCARBAZIDE

AND

DIPHENYLCARBAZONE

191

COMPLEXES

The infrared spectrum of the sodium salt did not contain the C=O band, whereas for diphenylcarbazone itself this band was found at 5.85 cc, lying in the region of the amide compounds (5.80-6.15 p). K~I,..

To evaluate

=

W+) WV (HzD)

HD- = anion), equal volumes of solutions of diphenylcarbazone in carbon tetrachloride were shaken with aqueous phases of various PEE values greater than 7.5. It proved to be necessary, even for water of AnalaR quality to add potassium djranide (up to IO- 4 M) to prevent complex formation of the reagent with traces of metal ions at these pH values. The ionic strength of the water phase was kept constant at 0.1 N NaC104. The system attained equilibrium within I min. ’ From extinction measurements on the carbon tetrachloride phase before (E) and after (E’) shaking, Kdise. was calculated:

(I-&D = diphenylcarbazone,

E’ B--n’-

Pccr.,(H+) (H+) + KOI~L

(H+) was measured after the equilibration. The water used was made oxygen-free by bubbling nitrogen through the solution. PH measurements were also made in a nitrogen atmosphere. Fig. 2 gives the percentage of carbazone in the organic phase as a

-PH

Fig. z. Partition

of diphcnylcarbazonc between carbon tctrachlorido in the pH range 7.0-10.5.

and water (Vcol,

=

VW,,,)

function of the PH. From these values we calculated &I~. to be (a.9 f: 0.3) -10-Q. In a previous short communication 10 erroneously the value (2.2 & 0~2). 10-8 was mentioned. The concentration of a saturated solution of the carbazone in water (PH = 1.00 with perchloric acid) was determined by extraction of the reagent with toluene; it proved to be 3.8-10-4M. DISCUSSION

Comparison of the spectra of diphenylcarbazone

in water and diphenylformazane Anal. Chim. Ada,

a7 (1962)

in

18%193

S., BALT, E. ,VAN DALEN

=92

toluene leads to the same conclusion as GRAMMATICAKIShas drawn for the alcoholic solutions. The carbazone in aqueous solution does not resemble the formazane in toluene solution. Solutions of diphenylcarbazone in carbon tetrachloride and toluene, however, give a different spectrum : the visible spectrum shows two absorption bands, a strong one at 450-470 m,u, and a weaker one at 550-570 rnp. In the spectrum of the aqueous solution these two maxima have weakened to z shoulders on the 300 rnp band. In toluene or carbon tetrachloride solutions diphenylcarbazone seems to resemble’ the formazane more than it does in aqueous or alcoholic solution. This may indicate that a considerable part of the carbazone is present in the enolic form (II) in carbon tetrachloride and toluene. In this case the absorption at 550-570 rnp that is missing in the anion and in the formazane, is probably due to the ketonic form (I). Concordant with this conclusion is the absence of the C=O band in the infra-red spectrum of the solid sodium diphenylcarbazonate, an indication that the enolic form is the only form present in the solid salt. BAMBERGER~has already proposed, and given evidence for, this structure for the sodium salt. In this case Kales. = z.g*ro-0 is not the true dissociation constant, because it is reasonable to assume that (I) will rearrange into (II) before forming the anion. If I-&,r is the enolisation constant for (1) s (II), then

The partition of diphenylcarbazone between carbon tetrachloride and water is strongly influenced by sulphate anions (Table II). The increase in the partition coefficient indicates a decrease in the solubility of the carbazone in sulphate solutions. Perchlorates have no influence; in this case, ~CCI, is constant at 7.5 -+ 0.5. From the data given, the solubility of diphenylcarbazone in water appears to be 3.7:,x0-4 (from ~~ccI~) or 2.7-10-4 mole/l (from $tOruonc)in 0.1-1 M NaClOlt. Direct measurement gives 3.8 - 10-4 mole/l, so for the toluene-water system the value found is too low, which indicates that p to1uenOwill decrease at carbazone concentrations of about 10-2 M. ACKNOWLEDGEMENT Some of the esperiments described were performed by Mr. TJ. HOMSMA AND Mr. J. KLEINE DETERS. SUMMARY Extraction cxperimcntsin the carbon tetrachloricle-water system for diphcnylcarbazoneabove pH 7.5 give a value of (2.9 =t: 0.3)*10- u for the dissociation constant. At lower PH values the partition

coofficicnts

in 0.x-1 M N&104.

were found to be 7.5 for carbon tetrachloridc-water and 39 for toluene-water The solubility of the carbazonc in water is 3.8 '10-4 M in acid pcrchlorate

medium. Spectra of diphenylcarbazone in water, tolucnc and carbon tetmchloride, of the anion in water and,of diphenylformazane in tolucne are compared. In the infra-red spectrum the C=O band was present in the cnrbazonc, but not in the sodium salt.

Rl%UMa Les auteurs o?t cffectudunc dtudc sur la diphdnylcnrbazone: chlorurc de carbone-cnu

extraction dans les systemes tbtraet toluhne-eau ; solubilitd dans l’eau ; mesurcs spectrophotometriques; Anal.

Cirim. Ada,

27 (19th)

x88-193

DIPHENYLGARBAZIDE

AND DIPHENYLCARBAZONE

COMPLEXES

193

ZUSAMMENFASSUNG Beschreibung einer Untcrsuchung iibcr das Verhalten von Diphcnylcarbazon im System Tetrachlorkohlenstoff-Wasscr und Toluol-Wasser mit Angabe dcr Vertcilungskoeffizientcn, Ulslichkeit in Wasser tind Absorptionsspcktrcn. REFERENCES 1 M. I?. CAZENEUVE, Ber., 25 (190x) 450. 2 E. RAMBERGER. hr.,44 (IgIl) 3743. 3 E. ~AMBERGER, R. PADOVA AND E. ORMEROD, Ann., 446 (1925) 260. 4 I?. GRAMMATICAKIS,CO~#& rend., 234 (x952) 528. 6 F. J, WELCHER; Ovgalric Analylical~Reagents, van Nostrand 1947, Vol. III, page 456 ff. 0 P. AND IL KRUIIHOLZ, Silz.ber. n knd. Wiss. Wien, 146 (2B) (x937) 431. 7 H.IRvING,S.J.H.COOKE,S.C. WOODGER AND R.J.P. WILLIAMS. J.Chem.Sod.,(rg4g) 8 E. B. SAN~ELL, J. Am. Chem. Sot., 72 (1950) 4660. B D.L. WRIGHT AND F. J. VANCMERI. Ilid. Eng. Chem., 53 (IgGr) 15. 10 E.VAN DALEN ANDSBALT, AnaL Chim. Acta. (xg61)507,

,

1847.

Anal. Chim. Acta, 27 (rgG2) x88-193

Short

Communications

A general formula foi the calculation of

pH

of acids’and bases

All the methods proposed for the calculation of the PH of aqueous solutions of acids and bases are characterised by different qifficulties. They refer only to the case of a strong or a weak, acid and there is a real need for a formula for the pr-x-calculation of a fairly strong acid or base. Moreover, different calculations have to be used for different acidity or basicity constants and original concentration, while in many cases the influence of the water is not taken into account. After a complete calculation in which the problem of the formation of protons was solved separately from that of the influence of the water, it is possible to propose a new general formula for the pH-CdCUhtiOII of all acids (with acidity’constant I<) at all concentrations (original’ normality N) ; the proton activity [H+J of the ,aqueous solution is given by

[H+] =

)IKN 2

)/K+qN---)lz ---

)

++i$

ir;-iR)’

+

s$*IO-‘~

(

The same formula is used for the calculation of the [OH-] activity of an aqueous solution of a base, replacing I’ by K’ (basicity ‘constant) and N by N’ (original normality of, the base). ’ : The origin of this formula will fully be discussed in a further communication. Laboratory of Analytical Chemistry, Faculty of, Medicine, University of Chent (Belgium) Received

A. CLAEYS

May 7th,‘Ig6z Anal. Chim. Acta, 23 (IgG2) 193