Proton relaxation rates in solutions MnCl2-CD3OH and MnCl2-C2D5OH are reported and from these data rotational correlation times for the solvation complexes are determined. Proton and deuteron relaxation rates for the hydroxyl, methylene, and methyl group in solutions of Mg(C104)2, CaCl2, NaC104, Nal, and KI in methyl alcohol and ethyl alcohol are reported, and correlation times for the various groups are determined. The various correlation times are compared with one another and, in those cases where they differ for a given solvation complex, intermolecular or intramolecular motions are postulated. The results are also compared with predictions derived from pertinent theories currently available. It is found that the description of the internal motions by the theory is not satisfactory in all cases.
Partial resolutions of a series of organic racemates' have been achieved by partitioning the racemates between an aqueous phase and an optically active ester of d-tartaric acid. A semiquantitative treatment of the data indicates that the observed results are in agreement with those predicted from the normal relationships dealing with solvent extractions. lthough the differences in chemical interactions port of the U. S . Army Research Office, Durham, in conducting this investigation. We also wish to acknowledge the contributions of M. S . Barry and N. Sartoris who conducted certain preliminary studies.Abstract : The reaction of methyl 3-amino-P-~-xylopyranoside (5) with nitrous acid effected a ring contraction to give methyl 3-deoxy-3-C-formyl-P-~-erythrofuranoside (6) as the main product along with small amounts of methyl 2-deoxy-2-C-formyl-~-~-erythrofuranoside (16). Reduction of the aldehyde function with sponge nickel to the diols 7 and 17 followed by esterification, acetolysis, and nucleoside condensation gave 9-(3-deoxy-3-hydroxymethyl-&(and a)-D-erythrofuranosy1)adenine (13) and 9-(2-deoxy-2-hydroxymethyl-P-(and a)-D-erythrofuranosy1)adenine (21). Intervention by a 1,2 ortho ester ion afforded a 5 : 1 ratio of 13b : 13a. No intervention by a 1,3 ortho ester ion was indicated by the 1 : 1 ratio of a and fi anomers in the 2-branched series. Double-resonance nmr was used to identify the 3-branched series.n recent years, branched chain sugars have been dis-
the neighborhood of 13-14 kcal/mol can be ascribed to amide torsional barriers. Our results, however, are in striking contrast with those reported for the analagous compound in which the methoxy groups are replaced by fluorine atoms. zb Unless accidental equivalence is responsible for the differences in the two systems, it would appear that replacement of fluorine by methoxy both raises the amide barrier and lowers the barrier to nitrogen inversionzb (or ring reversalzc). Experimental SectionN,iV'-Biscarboethoxy -3,3,4,4-tetramethoxy -1,2 -diazetidene was prepared as previously reported.6The nmr spectra were measured on a Varian A-60A spectrometer equipped with a Varian variable-temperature probe using ca. 10% solutions. Temperatures were determined using methanol spectra as described in the Varian Manual. Rate constants and equilibrium constants were determined by matching experimental spectra with theoretical spectra. The theoretical spectra were generated using Saunder's Many Site NMR Lineshape Program.7 This program allows the calculation of nmr spectra involving exchange between n sites (2 5 n 5 25) which must be uncoupled, but need not have the same population. The two "out" methoxy groups of Ib which are diastereotopic with respect to the "in" methoxy groups were treated as two separate isomers. Exchange was assumed t o be possible between l a and both sites in lb and between IC and both sites in Ib, but not directly between la and IC, nor between the "in" and "out" sites of l b . The chemical shift differences and the relative populations were temperature dependent and were determined by iterating to obtain the best fit.
It has been found that substituted diohloromethyl malonic esters react rapidly above 65°in inert solvents with one equivalent of ethoxide ion to give a-chloromethylene carboxylic esters in yields generally over 90%. The other products are diethyl carbonate and chloride ion, If two equivalents of ethoxide ion are SUMMARY It is shown that substituted dichloromethyl malonic esters react in inert solvent with one equivalent of ethoxide ion to yield -chloromethylene esters and diethyl carbonate: with two equivalents of ethoxide ion to yield diethyl carbonate and the corresponding -ethoxymethylene ester.The reactions of substituted dichloromethyl malonic esters with two equivalents of ethoxide ion in ethanol produce diethyl carbonate, a-ethoxymethylene esters, ethyl orthoformate, and traces of the ester corresponding to the hydrolysis and decarboxylation of the original substituted malonic ester.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.