Fragmentation of tertiary alkyl carbonium ions in sulphuric acid : steric effects.

1971 ◽  
Vol 12 (18) ◽  
pp. 1349-1350 ◽  
Author(s):  
J.E. Dubois ◽  
J.S. Lomas ◽  
D.S. Sagatys
Keyword(s):  
Sulphuric Acid ◽  
Steric Effects ◽  
Carbonium Ions ◽  
Tertiary Alkyl

Studies of the Wallach Transformation. II. Steric Effects in Some Symmetrically Disubstituted Azoxybenzenes

1951 ◽  
Vol 4 (2) ◽  
pp. 185
Author(s):  
PH Gore ◽  
GK Hughes
Keyword(s):  
Sulphuric Acid ◽  
Important Influence ◽  
Steric Effects ◽  
Hydroxyl Group ◽  
Azoxy Compounds ◽  
Point Of Entry ◽  
Substituent Group

Study of the behaviour of symmetrical azoxy compounds in the Wallach Transformation shows the important influence of size of a substituent group ortho to the point of entry of the hydroxyl group.�The various processes known to occur in a solution of azoxybenzene in sulphuric acid are discussed.

A SPECTROMETRIC STUDY OF THE REACTIONS OF KETOSTEROIDS IN SULPHURIC ACID

1958 ◽  
Vol 36 (11) ◽  
pp. 1221-1236 ◽  
Author(s):  
Hilda F. Goldberg ◽  
J. H. Linford
Keyword(s):  
Sulphuric Acid ◽  
Absorption Spectra ◽  
Room Temperature ◽  
Addition Reactions ◽  
Spectrometric Study ◽  
Double Bonds ◽  
Carbonium Ions ◽  
Protonated Molecules

The reactions of C3 ketosteroids in concentrated sulphuric acid and in fuming sulphuric acid have been studied by following the development of their absorption spectra. The results are attributed to protonation of the C3 keto oxygen in 98%–100% acid, and to removal of the C3 keto oxygen in fuming acid. These reactions proceed at a higher rate at 100 °C than at room temperature, but the reaction is the same.It is suggested that in the presence of conjugated protonated ketone, double bonds take part in addition reactions to form the hydrogen sulphates. In the absence of conjugated ketone, or when the acid is diluted to prevent the occurrence of protonation, double bonds react with protonated molecules of acid solvent, or of diluent, or of added reactive compounds, to form carbonium ions.

Stabilities of Carbonium-Ions. IV. Steric Effects in the Solvolysis of Substituted Diphenylmethyl Chlorides

1986 ◽  
Vol 39 (4) ◽  
pp. 625 ◽  
Author(s):  
R Bolton ◽  
RE Burley ◽  
NJ Williams
Keyword(s):  
Electronic Effect ◽  
Substituent Effects ◽  
Methyl Chloride ◽  
Steric Effects ◽  
Methyl Groups ◽  
Hydrogen Atoms ◽  
Carbonium Ions ◽  
Rate Of Reaction ◽  
Resonance Stabilization ◽  
Planar Transition

The replacement of ortho-hydrogen atoms by methyl groups in diphenylmethyl chloride has three distinguishable results upon the rate of solvolysis . Firstly, the alkyl groupactivates by its electronic effect; secondly, steric interactions diminish all observed substituent effects regardless of the position of the substituent in the aryl system; and thirdly, steric acceleration of the solvolysis can be seen in the rate of reaction of bis (2,6-dimethylphenyl)methyl chloride. The ortho-methyl substituents inhibit the formation of the planar transition state necessary to allow the greatest resonance stabilization by the aryl substituents of the incipient carbocation. Greater degrees of twist are reflected both in the variations in the rates of solvolysis of the poly(orthomethyl ) diphenylmethyl chlorides and in the consistent fall in the value of p+ with successive ortho-substitution.

PROTONATION OF THE CARBONYL GROUP: II. THE BASICITIES OF SUBSTITUTED BENZALDEHYDES

1959 ◽  
Vol 37 (4) ◽  
pp. 664-671 ◽  
Author(s):  
K. Yates ◽  
Ross Stewart
Keyword(s):  
Sulphuric Acid ◽  
Carbonyl Group ◽  
Spectrophotometric Method ◽  
Ultraviolet Absorption ◽  
Steric Effects ◽  
Acid Media ◽  
Substituted Benzaldehydes ◽  
Group Ii

The basicities of seven meta- and para-substituted benzaldehydes have been determined by a spectrophotometric method in sulphuric acid media. The simple Hammett relation does not hold for these bases but a good correlation exists between [Formula: see text] and σ+. The effects of substitution on the wavelengths of maximal ultraviolet absorption in benzaldehyde are compared with those in acetophenone.The basicity of o-tolualdehyde was determined in an attempt to estimate the steric effects of ortho substitution. The effects of symmetrical trisubstitution on the basicity of benzaldehyde and acetophenone are compared and discussed.

A SPECTROMETRIC STUDY OF THE REACTIONS OF KETOSTEROIDS IN SULPHURIC ACID

1958 ◽  
Vol 36 (1) ◽  
pp. 1221-1236
Author(s):  
Hilda F. Goldberg ◽  
J. H. Linford
Keyword(s):  
Sulphuric Acid ◽  
Absorption Spectra ◽  
Room Temperature ◽  
Addition Reactions ◽  
Spectrometric Study ◽  
Double Bonds ◽  
Carbonium Ions ◽  
Protonated Molecules

The reactions of C3 ketosteroids in concentrated sulphuric acid and in fuming sulphuric acid have been studied by following the development of their absorption spectra. The results are attributed to protonation of the C3 keto oxygen in 98%–100% acid, and to removal of the C3 keto oxygen in fuming acid. These reactions proceed at a higher rate at 100 °C than at room temperature, but the reaction is the same.It is suggested that in the presence of conjugated protonated ketone, double bonds take part in addition reactions to form the hydrogen sulphates. In the absence of conjugated ketone, or when the acid is diluted to prevent the occurrence of protonation, double bonds react with protonated molecules of acid solvent, or of diluent, or of added reactive compounds, to form carbonium ions.

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