Effect Of N-substituents Research Articles

Relative concentrations of zwitterionic and uncharged species in catecholamines and the effect of N-substituents.

The relative concentrations of zwitterionic and uncharged species for the series of N-substituted catecholamines (I, R1 = R2 = OH; R = H, Me, Et, i-Pr, t-Bu) are derived from the pKa data published in 1962 by Sinistri and Villa. The concentration ratios, represented by the tautomeric equilibrium constant Kt, show a definite trend and are respectively 1.8, 4.3, 4.7, 4.7, and 7.1. These values suggest that any mechanism of action involving proton transfer, which might transform the zwitterion into the uncharged form, would be most favorable for norepinephrine and least favorable fo the t-Bu derivative.

Complexes of tertiary amides with acetylacetonates of oxovanadium(IV) and copper(II) in methylene chloride solution

The stability constants for adducts of tertiary amides to oxovanadium(IV) acetylacetonate and to copper(II) acetylacetonate were determined in order to study the effect of various N-substituents of tertiary amides on their complexing ability. Information about the possible orientation of the NN-dimethylacetamide molecule in the VO(acac) 2DMA complex could be received by NMR spectroscopic work from broadening of the resonance lines of the N-methyl groups.

Iminodithiocarbonates. III. Reactions with Some Electrophiles and the Structural Effect on Nucleophilic Reactivities and Basicities

Abstract With a view toward demonstrating the structural effect on the reactivity of iminodithiocarbonates, the reactions of some electrophilic reagents with the following four iminodithiocarbonates have been studied; 2-methylimino-(IVa) and 2-phenylimino-1,3-dithiolane (IVb) and S,S′-dimethyl-N-methyl-(Va) and S,S′-dimethyl-N-phenyliminodithiocarbonate (Vb). Cyclic IVa and its N-ethyl homologue reacted with an equimolar amount of phenyl isocyanate at room temperature giving 1:2 cycloadducts. However, the other imino compounds (IVb, Va, and Vb) did not react at all even at elevated temperature. All these imino compounds reacted with acid chlorides to afford the corresponding N-acyliminium salts which could, in some cases, be isolated; however the rate of formation of the salts varied significantly with the structure of the imino compound. Some reactions with alkyl halides and phenyl isothiocyanate were also attempted. From the present results and those previously obtained on their reactions with epoxides and with ketenes, it has been concluded that the nucleophilic reactivity of the imino compounds increases in the order Vb<Va<IVb<IVa. Furthermore, it was found that the basicity of the imino compounds increased in the order Vb<IVb<Va<IVa. The observed ring effect and N-substituent effect on the reactivity and basicity of the imino compounds are discussed in connection with similar effects on the stability of closely related tri(hetero)carbonium ions, i.e., bis(alkyl thio)-dialkylaminocarbonium ion (I).

Reactivities of radiation-protective aminoalkylisothiuronium salts. IV. Stability of N-ethyl derivatives of 2-aminoethylisothiuronium salt.

The effect of N-substituent on the stability in an aqueous solution of AET was studied. By the substitution, both the transguanylation and the cyclization were hindered. The reactive species of N-Et-AET, and probably of N'-Et-AET, for the transguanylation is the monoionic conjugate base. N'-Et-AET, being relatively stable in the presence of less than one equivalent alkali, may be dissociated through the two-steps ionization to the neutral conjugate base, which would be considered as one of the reactive species. The degree of the transformation of N-ethylated AET derivatives was as follows ; the transguanylation in the presence of 0.5 equivalent NaOH for 4 min at 15° : AET ; 0.95, N'-Et-AET ; 0.84, N'-Et-AET ; 0.27. the cyclization in 3 days at 30° : AET ; 0.95, N'-Et-AET ; 0.36, N'-Et-AET ; 0.29. The relationship between the transguanylation and the pH drop in the solution was discussed.

Effect of N-substituent on the protein-binding of carcinogenic aminoazo dyes.

Effect of N-substituent on the protein-binding of carcinogenic aminoazo dyes.

Photolysis of cyclohexadiene imides: N-substituent effects and bicyclo[2,2,0]hexene formation

Photolysis of cyclohexadiene imides: N-substituent effects and bicyclo[2,2,0]hexene formation

Pyridinium Complexes. IV. The Effect of N-Substituents on the Position of the Iodide Charge-transfer Band

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPyridinium Complexes. IV. The Effect of N-Substituents on the Position of the Iodide Charge-transfer BandEdward M. Kosower, Dieter. Hofmann, and K. WallenfelsCite this: J. Am. Chem. Soc. 1962, 84, 14, 2755–2757Publication Date (Print):July 1, 1962Publication History Published online1 May 2002Published inissue 1 July 1962https://doi.org/10.1021/ja00873a023RIGHTS & PERMISSIONSArticle Views101Altmetric-Citations46LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (342 KB) Get e-Alerts Get e-Alerts

Heterochain polymers Communication 1. effect of n-substituents on the properties of polyamides derived from 4,4?-methylenedianiline

1. Polyamides were prepared by condensation of a mixture of 4,4'-methylenedianiline and 4,4'-methylenebis [N-alkylaniline], on the one hand, with adipic, azelaic, or sebacic acid, on the other, in order to give products in which amide hydrogen was replaced to various extents by methyl or ethyl radicals. 2. It was shown that with increase in the extent of the replacement of Amide hydrogen by methyl or ethyl, the softening and melting points of the polymer fell. 3. It was shown that the melting point fell also as the molecular weight of the dicarboxylic acid increased. In the case of azelaic acid the “odd-even” factor did not have its usual effect. 4. It was shown that the properties of polyamides derived from aromatic diamines are determined primarily by the extent of hydrogen bonding between amide groupings, whereas interaction between aromatic nuclei is of secondary importance.