Julie 3, 1933
:i153
NOTES
hetero-atoms is small and can be shown4a5to exert only a second-order effect on charge distribution. Since the orbitals of the central atom of the -X@ group in IV (like N in -N(CH3)a@)are used in four sp3-bonds, the a-electron resonance integral for the C1-X@ bond was assumed to be zero. Thus, the only electrical effect considered for -X@was inductive generation of a positive charge on Cl, increasing the electron affinity of that atom and to a lesser extent the electron affinities of C2 and ( 2 6 . The values of the parameters used are summarized in Table I. The resulting r-electron charge distributions in the /)arts-ainino derivatives are shown in VII, VI11 and IX.
on Cq as postulated previously.' The failure of pamino- and p-dimethylaminophenyltrimethylainmonium salts to be weak bases relative to the corresponding m-isomers is thus regarded as strong experimental evidence against important preferential induction by the trimethylammonium group of charged centers in the 2- and 3 - p 0 s i t i o n s . ~ ~ > ~ (7) (a) J. D. Roberts, E. A. McElhill, R . A. Armstrong. 1 ~ 1 s JOURNAL,71, 408 (1960); (b) J . D Roberts, R . A . Clement a n d J J . Drysdale, ibid., 75, 2181 (1951). ( 8 ) A somewhat different interpretation recently has heeii exlxessed b y C. K. Ingold, "Structure a n d Mechanism in Organic Chemistry." , 234, i 3 2 . Cornell University Press, I t h a c a . S . Y . pp.
CONTRIBUTIOX S o . 1953 GATESA N D CRELLISLABORATORIES CALIFORNIA IXSTITUTEOF TECHNOLOGY PASADEXA 4, CALIFORNIA
Reaction of Fumaric Acid with Cysteine
m
-c>-
Q-Y +0.264 -0.031 f0.055
+0.106
BY LEOPISE ASD CARLL. PEACOCK RECEIVED FEBRUARY 7, 1955
,--,-0.0391fJ=z
+0.046
H2N
rn -0.424
Ix TABLEI ~ ( I I J L O MINTEGRALS ~ U S E D Ih' CALCULAI'ICJSS
System
I \'
alld
\.I1
\. atid \-I11
\.I alld
1s
\ . I l , \.I11
,llltl
Coulomb integral
CI
=
Y
= =
c 1
=
cp
+ 0.3Op c, = + (I.U$ CY
cy
- 1.40p 01 - 0.14/3
CY
Z =
cy
c,
cy
IS s
= =
CY
c1 =
CY
+ 0.80p + 0.088 + 2.008" + 0.20p
1\--1x
Carbon atoms not otherwise tlesignated = CY Thc w l u c chosen for the coulomb integral of nitrogen 20 conimonly is used, alis not critical; the value of CY though it is probably not the best value for n i t r ~ g e n . ~
+
The calculated charges on the amino nitrogens for VI I-IX are essentially the same.6 Furthermore, the magnitudes of the calculated resonance energies for IrII-IX and the corresponding anilinium ions indicate t h a t compounds with charge distributions like VII-IX should have practically equal base
I
are calcustrengths. Thus, -X@, --I7or -C=Z lated to be equally effective in causing delocalization of para-amino electrons provided that C4 initially has the same charge in each case. It is concluded, therefore, that so far as the LCXO method is concerned, the relative basicities of amino groups para located with respect to electron-attracting substituents provide a reasonable measure of the charge ( 5 ) G. W. Wheland, THISJ O U R N A L , 64, 900 (1942).
I
( 0 ) T i t h e charges O I I C ? , C , .tnd Cti in t h e -X@ a n d -C-Z syqtern< .+re iiiitiallv t(l 1 . i irihte.id < > l+ O 0: i a n rlertrtrn charge, t h e culrtilitrrl charar-: 1)11 a Piii.,i-alninc, g r o u p are aKaiii i,ractically equal i , i i i i , r ~ , ~ i i i i : i li ~ - 0l ~. 1 - I ( t i U I I electr,,ii c h a r r r ) A c o i ~ i t ~ u r a l ~calcule I:I~I~III II:~L. n , > tlxrii in:idr i < >trh e -Ysgstriii. 1,111 tlirrr i b I I O re V Y I X ' L . I ( 1 1 tt 1 1 1 ~ . rr\i111 \\o111,1 llr rlitrrrent.
In recent studies of growth requirements of the yeast phase of Histoplasma capsulatum in liquid snedia,' it was observed that the presence of fumarate in a cysteine-containing medium did not affect growth of the fungus when the medium was sterilized by filtration. When the medium was autoclaved, however, growth was completely inhibited. Substitution of pyruvic acid for fumarate completely inhibited growth whether the medium was sterilized by heat or by filtration. These results appeared to demonstrate a requirement of the fungus for -SH groups in the medium, since the reaction of pyruvate with cysteine in the cold' and the reaction of niercaptanswithunsaturated compounds3 are known. Although Morgan and Friedniann4 have reported the reaction of maleic acid with cysteine a t low temperatures, fumaric acid did not react with cysteine under their conditions. The amorphous addition product of maleic acid and cysteine was isolated by these workers and was identified as S-cysteinosuccinic acid. Because fumaric acid and cysteine are used in the preparation of certain culture media and in many biological systems their reaction a t elevated temperatures is reported here. -4 simplified procedure for the isolation of S-cysteinosuccinic acid as a crystalline salt of acetic acid asid some of the properties of this compound are also given. Experimental Ten grams of L-cysteine (free base) and 11.3 g. of fuinaric acid were added t o 200 ml. of 95% ethanol. The mixture was heated t o near boiling until the reactants dissolved and the presence of -SH groups could no longer be detected with nitroprusside and strong alkali. The time required for the reaction t o go to completion was approximately two hours. The ethanol lost by evaporation during this time was replaced with water. The solution was placed in a refrigerator a t 5" overnight. The following morning, any cystine or fumaric acid which crvstallized from solution was filtered off and the volume of the filtrate was reduced to approximately 25 ml. by vacuum distillation. One hundred ml. of distilled water was added, the solution was cooled to ;io, arid the e y c t w fuiri:iric a c . i t l iv1iic.h crystallized from solu-
3154
VOl. 77
SOTES
tioii was filtered off, and the filtrate lyophilized. Approximately 20 g. of a n amorphous hygroscopic product was obtained. The product was added t o 100 ml. of glacial acetic acid, heated to 95" and kept warm until crystalline. After cooling t o room temperature, the product (18 g . ) was filtered off and was washed several times with ether. The compound was recrystallized as bundles of microscopic needles from approximately 50 times its weight of hot glacial acetic acid. The compound is assumed to be the acetic acid salt of S-cysteinosuccinic acid. '4nal. Calcd. for CgH,:NOsS: C, 36.47; H , 5.05; S, 4.88; S, 10.78. Found: C, 35.90; H , 5.10; X, 4.85; S, 10.77. ilfter drying over CaClp and KOH for two weeks, the total acid equivalency of a sample based on a mol. wt. of 297 was 2.88 (theory 3.0), equivalents volatile acid 0.85 (theory 1.0), u i d equivalents non-volatile acid (calculated) was 2.03 (theory, 2.00). Lpon heating the crystals became moist at 118 to 120'; they contract from 120 to 124", and then swell until they decompose with bubbling a t 132 to 134". The compound is very soluble in ethanol and water but only slightly soluble in ether. I t gives a negative -SH or -S-Sspot test but a positive test for thioether5and a positive ninhydrin test for amino acids. Although the addition of sterile fumaric acid to agar niedia containing cysteine stimulates growth of small inocula of the yeast phase of Histoplusma capsulatzim on agar media,6 the addition of the S-cysteinosuccinic acid salt instead of fumaric acid has no effect. I n liquid media the compound does not substitute for the cysteine requirement.
Acknowledgment.--Appreciation is expressed for the helpful suggestions given by Dr. Evan C. Horning for the isolation and identification of the fumarate-cysteine addition compound. ( 3 ) G. Toennies a n d J. J. Kolb, Anal. C h e m , 23, 81'3 (1951) (6) L. Pine, unpublished results.
1,ABORATORY OF I&-FECTIOUS NA~IONAL MICROBIOLOGICAL I NAlIONAL INSTITUTES O F HEALTH BETIIESDA, MD.
crystallized from 20 nil. of n-butyl alcohol dnd after filtration the crystals were washed with a small amount of ether. All of the derivatives crystallized in the form of fine white needles with the exception of the two noted in Table I. ill1 melting point5 are corrected.
THIOESTERS O F
Rlercdptan used
DOWSISG~ RECEIVEDFEBRUARY 2, 1935
lye have reported p r e v i o u ~ l ythe ~ ~ use ~ of 3,-1,.5triiodobenzoyl chloride for the identification of cellosolves, carbitols and alcohols. The increasing use of mercaptans has prompted us to extend the use of this acid chloride to the identification of these compounds. The acid chloride was prepared by the method previously d e ~ c r i b e d . ~All of the mercaptans were obtained commercially. Experimental IVith all but t w o of the mercaptans, 1 nil. of the mercaptan was added t o 1 g. of the acid chloride in a 15-cm. test-tube and gently heated with a micro-burner for 10 minutes. Methyl and isopropyl mercaptans, because of their low boiling points, were treated differently. I n these two cases 1 g. of the acid chloride was dissolved in 50 ml. of ether, 1 g. of the mercaptan added and the solution was allowed t o stand far 10 minutes. It was then heated for 5 minutes, the ether cvaporated and the residue crystallized from a solvent. 'The lower molecular weight thioesters were crystallized from 10 ml. of either methyl or ethyl alcohol. T h e higher molecular weight aliphatic and the aromatic thioesters were -
~~
~-
( 1 ) 'Taken f r o m theses submitted in partial fulfillment for t h e
M.S.
degree. ( 2 ) V O'Donnell and R . Carey, THISJ O U R N A L , 68, 1865 (1946) l:O I ) O'DonneIl, J. K e l l e y , R . O'hlalley and R. I J p h a m , ihicl., 7 0 , l t ; i i U!l48), ( 1 ) C . Rlrtnirir iind I . ITitntrr. .l. O r q . < I i p i r i , , 6, .iOX (IO4I)).
Yield, SI p , ' C
yo
Formula
Iodine, '6 Calcd Found
71.56 133.6-154.6" 43 M e thy1 68.38 37 n-Propyl 97.8-98.8" 68.40 28 15opropyl 133 ,4-15*5" 66.96 48 n-Butyl 90-91.4" 37 66.30 Isobutyl 89.5-90.8" 64.63 83 .2-84.4"' :3 4 n-Amyl 63.63 n-Hexyl 64.3-6.5 .2" 49 62.13 11 7n-70. sb n-Heptyl 60.50 46 n-Octyl 67-68.2'' 59 . 0:1 71)-70.8" 64 n- Sonyl _58.119 *>,I 76-77. 2h u-Decyl 57,118 78.6-79.8" 62 ti-Undecyl 53.20 7 5 .4-78.8' 33 tz-Dodecyl n-Tetra53,iti 86 4-87 43Y decyl 51.65 91 0-91 8" 62 Hexadecyl o-Thio30 CliHgOSI3 62.83 6 2 . 4 4 cresol 9s.4-99 , 0" 116,2-117 . 0' 60 CiiHgOSI3 62.83 6 2 . 8 8 Benzyl &Phenyl61.62 63 ethyl ru-Phenyl59.83 t5$) propyl b Ethyl alcohol as solvent. ( 8 hIethX1 alcohol a s solvciit. v-Rut!-l 'ilcohol :ii solvelit. White plates. e White gr:tnules. I 1E P A K T 11E A , I
3,4,5-Triiodobenzoyl Chloride as a Reagent for Identifying Mercaptans B Y DAVIDC. O'DOSNELL,HENRYA. MARIAXIAND DENS J .
TABLE I ~,~,~-TRIIODOBEN ACID ZOIC
(1 F
C I I E M I ~Y ~ R
Bos r o s C I)LI.EGE CHESTSTTHILI., 67,~ Z A S S .
Preparation of Pure 2-Aminonitropyridines and 2-Aminonitropicolines. Rapid Separations by Sublimation B Y LEWIS9. PINOASD ITINFIELD S. ZEHRCSGIIlI IZECEIVED DECEMBER 16, 1934
Considerable information exists on the nitratioii of 2-aminopyridine and the 2-aminopicolines. However, there is reported no simple, rapid method of separating the isomeric nitroamines of the pyridine series. This paper gives the results of a study of sublimation as a means of rapid, clean separation. Separation of aminonitropyridine has been xcomplished by steam distillation and fractional crystalli~ation.~*~b,3 I n some instances, no attempt a t separation was made until the mixture of isomers had completed a series of additional reactions after which one modified isomer was recovered and the other l ~ s t . ~ , ~ Separation by sublimation seemed feasible since a vicinal nitroamine is capable of chelation with a resulting increase in molecular symmetry and vapor (1) From a thesis submitted t u t h e faculty of Allegheny College in partial fulfillment of t h e requirements for t h e M.S. degree, June, 1954. (2) (a) A . B. Chichibabin and B. A. Razorenov, J. Russ. P h y s . Chetn. Soc., 47, 128fi (1915); .I. Cheiu. S O C . , 108, I , 992 (1915); ( b ) T C ~ ~ I I I Wa nI lIi I C r . o r x L r d d TRIS J O I J R X A I . . 6 4 , 1 6 ~ i31 ~ 1 2 ) . G31 \ I \ l'liilli~i~. ./ i'iri, 'IC), , I:? ~ 1 ~ l L l ) .
w.
c
