Hemihydrochloride

CARBOXYMETHOXYLAMINE HEMIHYDROCHLORIDE (Acetic acid, aminooxy-, hydrochloride)... 

Fig. 2.2 a-c. Early examples of three-center bonds from neutron diffraction studies, a In a-glycine [65] b in glycine hemihydrochloride [66] c in perdeuterated violuric acid [67]... 

Further evidence for three-center bonds came from the X-ray analyses of the P and y forms of glycine [71, 72] and glycine hemihydrochloride [66], but the first definitive neutron diffraction evidence for the existence of the three-center bond, as a relative rarity, was from the 1964 crystal structure analysis of perdeuterated violuric acid [67], the hydrogen-bond geometry of which is shown in Fig. 2.2c. In 1968, Donohue reviewed examples of crystal structures where there was good evidence for the existence of three-center bonds [73]. 

The effect of close stacking in a crystal structure is illustrated by the hemihydrochloride structure of 9-ethylguanine (35) in which one form is protonated and the other hydrogen bonded between the N-7 positions by a bond (2.637 A) which is the shortest so far observed (75AX(B)2862). The hydrobromide of 9-methylguanine analogously has the 7H structure (36) (64AX126). There can be no certainty, of course, that such a structure would have any relevance in solutions of the compound. 

Confirmation of the structural revision of vindolinine was obtained by single-crystal X-ray crystallography of the hemihydrochloride hemiper-chlorate which crystallized in the C2 monoclinic space group (73). 

Figure 11.2 Chromatograms of cefmenoxime hemihydrochloride (CMX) and cefotiam dihydrochloride (CTM) in (A) distilled water, (B) serum sample, and (C) acidified serum sample. Mobile phase 0.08 M SDS-8% 2-propanol in 0.047 M phosphate buffer at pH 3.3. The figures over the peaks represent the retention times. Reprinted from Ref 13 with permission of the American Chemical Society.

C18H20N2 f trans-3,8-Diphenyl-1,2-diaza-(E)-1-cyclooctene, 42B, 195 Cl8H35CIN2O2, Pelargolactam hemihydrochloride, 41B, 308 Cl9H17NO, 3-(Diphenylhydroxymethyl)-3H-azepine, 39B, 192 C19H2 2CINO, DL-1-Benzyl-5-phenyl-1-azacycloheptan-4-one hydrochloride, 40B, 240... 

C2oH2eBr2N203, 3,7-Dihydroxy-1,5-bis(p-bromophenyl)octahydro-1,5-di-azocine ethanolate, 42B, 195 43B, 319 C20H26N2O6S2/ cis-1,5-Bis(toluene-p-sulphonyl)-3,7-dihydroxy-octa-hydro-1,5-diazocine, 41B, 309 C20H39CIN2O2/ Caprinolactam hemihydrochloride, 41B, 310 C21H18CI2N2O2/ 1,4-Bis(p-chlorobenzoyl)-5-methylene-7-methyl-2,3,4,5-tetrahydro-1H-l,4-diazepine, 43B, 320 C2iHi8N2O3/ 5-Acetyloxy-1-benzoy1-6-methyl-7-phenyl-1,3-diazepine, 44B, 226... 

An alternative strategy relies on differing crystal sizes of the two reaction products, which therefore can be successfully separated. For example, in the resolution of DL-DOPA and its hemihydrochloride DL-DOPA 0.5 HCl, the following reaction occurs ... 

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