NOTES
Oct., 1961
1903
on the CH2 m-hich would reduce the shielding, or electric dipole moments of nitrate esters. Cowley the presence of positively charged zinc ion distorts and Partingto~i~ and de Kreuk3 measured the the bonding electron orbitals about the CH:! pro- moments of several nitrate est.ers, but, apparently, tons and generates a paramagnetic shift which is there is no published work on an extended series of in the direction of decreasing field. Li, et u Z . , ~ dinitrate esters. Measurements were made, therehave shown that the coordination sites in GG- fore, on benzene solutions of several dinitrate esters. toward zinc are the terminal amino group and the Experimental peptide oxygen in the immediately adjacent amide Materials.-Ethyl nitrate (East,man Kodak) was purified group. Since in GG- one of the CH2 groups is \)y ,distillation through a 20-cm. column packed with glass situated between t,he two coordination sites, one helices. All other esters were obtained from the research of this Station. 2,2-Bis-(nitroxymethpl)-3might, expect unequal shifts upon formation of a laboratories nit roxy-1-propanol was purified by chromatography on chelate and this corresponds to the observations. silica gel. The other nitrate esters were purified by distilFrom Table I it also is seen that when MgC1, 1:ttion a t reduced pressure. All of the nitrate esters wcrc is added to GG-- the corrected downfield chemical stored over silica gel in stoppered flasks. Solutions \\-ere with thiophene-free benzene4 which was dried with shifts produced are 0.08 and 0.14 p.p.m. The .hIg prepared hydride.6 chelate of glycylglpcinate is less stable than the Zn calcium Apparatus and Procedure.-E1ect)ric nioments were' chelate (log kl = 3.4 and 1.3,yrespectively, for Zn dctermined from benzene solutions a t 25". Dielectric coiland Mg chelates with GG-). The weaker binding stants were measured by a heterodyne beat, method with :$ ed in the smaller chemical shift crystal controlled oscillator similar in design to the apparatus by Hudson and Hobbs.0 The cell consisted of frequencies when MgC1, replaces tlescrihed t wn concentric gold-plated brass tubcs to which glass tuhw %nC12. were soldered at either end. The spare between the tiilws It is seen front Table I that in going from GG- W M provided with inlet and outlet, tubes which pcrmittcd to ZriGG and t'o MgGG, the effect on the chemical connection t o increased or diminished pressure. A calic:d precision condenscr, General Radio Type 72 shift for the second CH, is greater than for the brat was used in parallel with the cell and the low capaci first CH,. From the above discussion regarding rangc of 25 to 100 ppf. was employed. Purified benzen binding sit,es jn M - toward the metal ions, we IINYI to ca,librate t,he cell. Temperature was controlled by come to the conclusion that of the two CH, fre- niiuns of a tiiermostal; jacket on the outside of the rtsil. were measured with a modified Ostwald pycquencies in GG-, t8hesignal at 6 = 4.25 comes from Dimities l~orneter'and refractive indices with an Abbe ~efrnctonittrr. the CH2 adjacent to t,he carboxylate group, while XIeaeurements were made on a srries of five or six soliiThe signal at 6 = 3.84 comes from the C,H2 whic:h is lions ranging from 0.01 to 0.10 $1. Dicklectrir consta.nts and specific volumes --ere plotted against nGght, fraction of adjacent to the amino group. soliite and solute values for these quantitics wcrc ot~taineil In glycjncarnilde there is one CH2 group, hrnct. bl. the method of least squares. Molar rofract,ioxi,;.Rn,wcw only one (31, frequency. The change in 6, nft>er calculated from the solutio11 refractive index data. Solute, susceptibility correction is applied, amounts t o 0.36 po1:iriaations at, infinite dilution, P a ,were cnlculat rd from and (lipoic, p"p.ni. when Z n U 2 is added. This is in line with tht. Halverstadt arid Kumler monicnts from tjhe Debye equation I he iinding that Z i i chclates stroiigly to glyc*~iiep = 0.01281 x 10-16 ((Pm- K 2 ) T ) l h (1) (log k , 3.3'). The prot'ori niagn4ic resonance shift ineasiir~- w h w e 1' is the absolute temperature. The c:tlculattd d i t t :i meats alone (lo not provide uneyui\rocal evidcnc~: arc presented in Table I. The probable error in the niolxr is 1k0.03 and the probable error in the tlipnlr: for raompltrx formation. The n.ri1.r. spectra do, polarizations rnoinents is 3~0.03D . home\w, support t,he evidence derived from ot hrr Discussion and Results :vpcs of nirasurrtments, for instance, pI1 titrations. I Iigh resol~it~ion t i . n r . spectroscopy therefore repThe electric moment obtaimd for ethyl nitratr resciit)s an additional approach to t,he study of com- ( p = 2.96 D)is in agreement ait'h the value fouud plex forrnzttim, analogous to t>hemeasurement, of by Cowley and Part,ingtonZ ( p = 2.91 D ) for flit. .AWHEN(:E A N D
-4, J. hIA'rL-SZhO
i) .i. S. Erown. P. M. Levin and I?.
,t,:Ln,=,ln, .I, C i e , n
tcren,c:, imrj Deoeiop:nsnt Department, U . S. Naval I'ropslla?it ; ' i a x l , Indiwz Head, Maryland Heceitdd . J p r t l 15, l Y 6 l
ii! c:oniievtioir 1v:f.h .studies on plasti(hizatrio:ia.:itl t ic-izing agsciitx, iiitwcs1 was devclopcd i i i t ' r:
2988
r lR*2),
( 9 , ,i,R. P a r t i n R t i m ,
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