STUDIES ON THE NATURE OF THE RACEM.IC MODIFICATIONS OF OPTICALLY ACTIVE COMPOUNDS IN THE SOLID STATE Part VI. The Nature of the Racemic Modifications of 3-Nitro-p- toluidino-, 5-Iodo-o-toluidino-, 4-Nitro-o-toluidino-, Oxy-, 2-N;tro-p-toluidino-, 3-Nitro-4-chloroanilino-, 2: 5-Dichloroanilino. and 4.Chloro-o-toluidino-methylenecamphors By BAWA KARTAR SINGH, F.A.Se., AND RAM KUMAll TEWAlU (From the Panjab Umvunty 11131Uute 01 Chemistry, Lahore, and tM ChemiJtry Department. Unherlity 0/ Allahabad) Received February 24, 1947 IN this paper we have described our investigation of the nature of the racemic modifications of and its condensation products with 3-nitro-p-toluidine. 5-iodo-o-toluidine, 4-nitro-o-toluidine, 2-nitro-p- toluidine,3-aitro-4-chloroariiline,2: 5-dichloroaniline and4-chloro-o-toluidine. A racemic modification may exist in the solid state in one of the following three forms: (1) a mechanical mixture (conglomerate) of the d- and I-forms; (2) a true racemic compound of the d- and I-forms; and (3) a solid solution (mixedcrystal) of the optically active and opposite forms. Three methods have been devised for determining the nature of the racemic modification. Two of these methods based on measurements of freezing-point and solubility of the racemic modification and its mixtures with its d- or I-form are due to Roozeboom and Bruni," The third Bioche- mical Method, which depends upon the different actions of the optically active and opposite forms on micro- and higher-organisms, has been devised by one of us. 2 We have employed Roozeboom's freezing-point (melting-point) method in this investigation. A melting-point-composition-diagram for mixtures of the racemic modification and its d- or I-form is prepared: a racemic mixture of the d- and I-forms gives a diagram consisting of two curves with a minimum of temperature, the eutectic point (Type I); the racemic compound gives a diagram consisting of three curves with two minima (eutectic points) and a maximum of temperature lType II); and the solid solution (mixed crystal) of the d- and I-isomers will give a single continuous curve joining the melting-points of the optically active and opposite forms At 389
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STUDIES ON THE NATURE OF THE RACEM.ICMODIFICATIONS OF OPTICALLY ACTIVE
COMPOUNDS IN THE SOLID STATE
Part VI. The Nature of the Racemic Modifications of 3-Nitro-ptoluidino-, 5-Iodo-o-toluidino-, 4-Nitro-o-toluidino-,
By BAWA KARTAR SINGH, F.A.Se., AND RAM KUMAll TEWAlU(From the Panjab Umvunty 11131Uute 01 Chemistry, Lahore, and tM ChemiJtry
Department. Unherlity 0/ Allahabad)
Received February 24, 1947
IN this paper we have described our investigation of the nature of theracemic modifications of o~methylenecamphor and its condensation productswith 3-nitro-p-toluidine. 5-iodo-o-toluidine, 4-nitro-o-toluidine, 2-nitro-ptoluidine,3-aitro-4-chloroariiline,2: 5-dichloroanilineand4-chloro-o-toluidine.
A racemic modification may exist in the solid state in one of thefollowing three forms: (1) a mechanical mixture (conglomerate) of thed- and I-forms; (2) a true racemic compound of the d- and I-forms; and(3) a solid solution (mixedcrystal) of the optically active and opposite forms.
Three methods have been devised for determining the nature of theracemic modification. Two of these methods based on measurements offreezing-point and solubility of the racemic modification and its mixtureswith its d- or I-form are due to Roozeboom and Bruni," The third Biochemical Method, which depends upon the different actions of the opticallyactive and opposite forms on micro- and higher-organisms, has been devisedby one of us.2
We have employed Roozeboom's freezing-point (melting-point) methodin this investigation. A melting-point-composition-diagram for mixtures ofthe racemic modification and its d- or I-form is prepared: a racemicmixture of the d- and I-forms gives a diagram consisting of two curveswith a minimum of temperature, the eutectic point (Type I); the racemiccompound gives a diagram consisting of three curves with two minima(eutectic points) and a maximum of temperature lType II); and the solidsolution (mixed crystal) of the d- and I-isomers will give a single continuouscurve joining the melting-points of the optically active and opposite forms
At 389
390 Bawa Kartar Singh and Raro Kumar Tewari
(l"yp: I[I). In the present investigation we have not come across an example of Type III.
The nature of the middle branch (Type II) often indicates the dr of stability of the compound; ii" the compound is sufficiently stable, t~,e middle branch forros the greater part of the whole curve and rises a~d falls abruptly. When the compound is extremely unstable, t•e middle branch of the curve is smaUer and is much ttatter in appearance. We have applir these considerations in indicating the degree of stability of the racemic f o T m s .
The dextro-, l~vo- and racemic-forms of the substances were prepared by methods already described, s The melting-point determit~ations were carried out by preparing ah Ÿ mixture of accurately weighed quanti- ties of the racemic modification and its d- or l-forro and determining the melting-point of the mixturo by the capillary-tube method. The melting- points (in ~ C.) are given in Tables I-VIII.
D~usSrON
3-Nitro-p-toluidz'nomethflenecamphor.--The melting-point determinations are given in Table I. The melting-point-composition-diagram 0Fig. 1) con- sists of two symmetrical curves with a eutectic point. This shows that the racemic modification is a true d/-mixture and confortas to Type I mentioned above.
5-Iodo-o-toluidinomethylenecamphor.--The melting-point dr237 axe given in Table II. The melting-point-composition-diagram (Fig. 2) consists of three curves with two eutectic points. Therefore, the racemic modification is a true d/-compound and confortas to Type II mentioned abow. It is very stable, and the range of stability is very large as the middle branch is very steep and occupies almost the whole of the diagram.
Rac, mie Modii~r ons of O~/itallj, Active Comlbounds--'- V l
t64"
162"
/ \ , ~
o / \ 50 )
I~ ) 46" / \
391
od| 20 4o 8o so tood/ 8o 60 40 2o o d l tood 60 60 40 20 od.o] 20 40 60 80 100|
Pe rcen/el~e CnmDosition F[G. 2. 5-lodo-o-toluidinomethylenr162
4-N'itro-o.toluiditwmethylenecamphor.~The melting-point determinations are given in Table III. The melting-point-composition-diagram (Fig. 3) shows that the raccmic modification is a true d/-compound Cl'ype II). The shape of the middle branch indicates that it is faJrly stable and that the range of stability is fairly large.
Oxymethylenecamphor.-The melting-point determinations are given inTable IV. The melting-point-composition-diagram (Fig. 4) shows that theracemic modification is a true dl-compound (Type lI). It is stable bu t therange of stability is small.
so"
82~
.
.1\ J
"r-, V '\ ./
l"""- V ~ ,.-
"od! 20 40 60 80 loodl 80 60 40 20 od
82°
84
~
.s 80oQ"
~ 11fII:
~ 16
~ 7~t
ilood eo 60 40 20 od,oI 20 40 60 eo IDolPercenta,ge CDmposition
are givenin Table V. The melting-point-composition-diagram (Fig. S) showsthat the racemic modification is a true dl-compound (Type II). It is stablebut the range of stability is small as is clear from the shape of the middlebranch of the diagram..
Racemic Modi/icagions of Ogbtically Active ComŸ 393
3-Nitro-4-chloroanilinomethyIenecamphor.~The melting-point determina- tions ate given in Table VI. The melting-point-composition-diagram (Fig. 6) shows that the racemic modi¡ is a true d/-compound (Type II). Ir is much less stable as the middle curve is flatter in appearance.
~ i�91 ~ �91 ~
216' ' 216"
;,o8' 2os ~
. \ / Y' 2og , 2or
~o,' ~ ~"~ ~"='~ ~ 2o4"
, o , ' / ~ ,oz" ~00 e! 00"
odl 2o 4o 60 80 loodl Bo 60 4o 20 odi ~ood eo �91 4o 20 odpl 20 4o co 80 I00!
Percentd~e CompositJon
Fzo. 6. 3-Nitro-4-cldoroŸ
2: 5-Dichloroanilbmmethylenecamphor.--The melting-point determinations ate given in Table YII. The melting-point-composition-diagram (Fig. 7) shows that the racemic modiflcation is a true d/-ccmpcund (Type II) of low stability and that the range of stability is small.
LA" t,tl ~
. [ 1~lg,~ ~ ,a |39o f
13 '5' L53" Od )0 4O ~ SO wodL eSO 6O 40 XO od! t o o d e m eo ~o 2o odpl ~o ,to Go so mol
r~e rcenf4~[e Corn~3~ion
F ~ . 7. 2 : 5 - D i c h l o r o a n i i i n o m e t h y l e n e c a m p h o r s
4-Chloro-o-toluidinomethfle~ecamphor.~The melting-point dete~z0iva~- tions are given in Table VIII. The meltingopoint-composition-diagram (Fig. 8) shows that the racemic moditication is a true d/-compcu~d (Tylc�91 II)
394 Bawa Kartar Singh and Ram Kumar Tewari
of little stability. The range of stability is very small as indicated by theflat nature of the middle curve•
1. Roozeboom, H. W. B.BruDi, G.Singh, B. K., and Perti, O. N.
--and Nayar. B. K. K.-- and Perti, O. N.
2. Bhatia, H. B., and Singh, B. K.3. Sinah. B. K., alld Tewari, R. K.
SUMMARY
The racemic modification of 3-nitro-p-toluidinomethylenecamphor is atrue dl-miJIture whereas the racemic modifications of S-iodo~-toluidino-_
4-nitro-o-toluidino-_ oxy-_ 2-nitro-p-toluidino-_ 3-nitro-4-chloroanilino-_ 2: Sodlchloroanilinc- and 4-chloro-o-toluidino-methylenecamphors are all truedl-compounds.
The stability of the racemic forms is also discussed.
We wish to thank the University of Allahabad. where this work \\!asdone. for the provision of research facilities.