NEWCOMPOUNDS
Dec. 20, 1952
coordinates are given in the following tables. The numbering scheme used to identify the atoms in the asymmetric unit should he clear frotn the accompanying sketch.
6303
with the value found in S S . ~A more complete description of this investigation will appear shortly. The authors wish to thank Dr. E. J. Cohn of Harvard University who kindly made available a sample of N,N'-diglycyl-L-cystine for this work. (2) B. E. Warren a n d J. T. Rurwell, J . Chcm. Phys., 3, 6 (1038).
CONTRIBUTION No. 1707 THEGATESA N D CRELLINLABORATORIES OF CHEMISTRY CALIFORXIA IYSTITUTE O F TECIINOLOGY PASADEXA 4, CALIFORMA
NEW COMPOUNDS BONDLENGTHSI N N,N'-DIGLYCYL-L-CYSTINE DIHYDRATE
Salts of 5-Aminotetrazole The salts listed in Table I were prepared by either of two s-s 2.04 Nl-OJ 3.31 methods: (1) Equivalent quantities of anhydrous 5-aminos-cs 1.86 N2-01 2 75 tetrazole and the appropriate anhydrous amine or free guanidine base were caused to react in a minimum volume Ca-G 1 52 s-2-01' 2 89 of hot, absolute methanol or ethanol; if the product did not C*-C1 1.55 N2-0* 2 75 crystallize upon cooling, a small volume of diethyl ether was c1-01 1 21 04-04' 2 91 added. (2) Equivalent quantities of 5-aminotetrazole c1-01 1.21 0, -0J 3.13 monohydrate and the appropriate carbonate or bicarbonate salt of the base were dissolved in a small volume of water; C2-N, 1 48 I 35 Average prohnblz error in dis- the solution was evaporated to dryness to give the salt. N1-G These salts were recrystallized from absolute methanol, c3-03 121 tances is 0.02 A. ethanol or mixtures of ethanol and diethyl ether. All of crc4 1.55 0 4 refers to the oxygen atom of these salts were very soluble in water and in general were also appreciably soluble in methanol or ethanol. Salts deC4-N2 1.46 the water of hydration. rived from very volatile bases were unstable and readily BONDANGLESIN N,N'-DIGLYCYL-L-CYSTINE DIHYDRATE dissociated into the free base and a residue of 5-aminotetrazole. For example, methylamine could be completely re8, 8, moved from its salt by heating at 80 to 100' for a few hours degrees Hydrogen bond angle degrees Angle or by evacuating continuously at room temperature for a 103 cI-NT-01' 85 s-s-C6 few days. For this reason the melting points of some of these salts were rather indefinite even when the sample was 105 CI-N~-OI 129 s-cI-c2 sealed in a capillary. 112 117 cry*-02 cs-c2-c1 11s C1-01-X4 143 Cs-Ct-Nt TABLE I 109 C1-01-N*' 96 c1-c2-s1 N--s 127 c1-01- x2 126 01-c1-02 SALTSOF 5-AMINOTETRAZOLE [RH]+ 11 C--T\"a 144 115 CB-OJ-NI C2-C1-01 140 118 c2-sr-03 Nitrogen,) YO c2-c1-02 R Formula M.P., O C . 0 Calcd. Found 122 C1-X1-03 96 C~-NI-C3 124-125 d Hydrazine' CH7N7 106 NI-CS-OJ 125 cs-03-04 , 72.38 72.51 Methylamine C2HaNe 118 121 03-04-04' cd-cs-03 Diethylamine CsHIdNs I 53.13 53.23 113 Average probable error in N1-CB-CI Ethylenediamine CIHI~NIZ 166-167 73.01 74.23 109 angles is '1 c3-c4-x2 49.38 49.43 CeHlrNa 176-178 Piperidine One of the many interesting features of this struc- Morpholine 48.81 48.81 C6HlzNs 126-127 ture is the long hydrogen bond (3.31 A.) existing Benzylamine CsHliNa 130.5-131.5 43.72 43.71 between the respective amide groups of molecules Guanidine 77.74 78.45 CrHsNs 126-136.5 related by the b repeat. Van der Waals repulsions Methylguanidine C ~ H I O N ~ 109-1 10 70.85 70.22 between the molecules involved seem to be respon- Phenylguanidine CIHIZXI 121-121.5 50.89 50.84 sible for the unusual length. This weak bond is Aminoguanidine C&.N, 93-95 79.21 79.10 accompanied by a slight non-planarity of the amide Benzalaminogroup of the molecule. The non-planarity, which guanidine C O H ~ ~ N145.5-146.5 O 50.99 51.09 corresponds to a rotation of approximately 6' about a The melting points are corrected. *Analyses by the N1-Cs bond, introduces a strain energy calcu- Margaret M. Mayfield. "This salt was first prepared by lated to be only 0.4 kcal./mole, however. The Howard W. Kruse, Inorganic Chemistry Branch, ChemisCalcd.: slightly long bond and the short C3-0~bond try Division, U. S. Naval Ordnance Test Station. , 10.25; H , 6.03. Found: C, 10.52; H, 6.17. 'Melts may also be a consequence of the weak N1-03 hy- C 112-117' with preliminary softening from about 95'. drogen bond. 1 Melts 114-118' with preliminary softening from about The disposition of hydrogen bonds about the 100'. Bond
R,JA.
Hydrogen bond
R,,.8,
c
terminal nitrogen atom leaves no doubt concerning the zwitterion nature of this peptide. It may also be mentioned that the C5-S-S-C~' dihedral angle is calculated t o be in 101' in good agreement
' 1-
INORGANIC CHEMISTRY BRANCH, CHEMISTRY DIVISION U. S. NAVAL ORDNANCE TESTSTATIONRONALD A HENRY CHINALAKE,CALIFORNIA RECRIVED JULY 2.5, lSFj2
