Bicyclo[3.2.0]hept-6-en-2-yl carbonium ion. 2-Methyl substituent effects

1975 ◽  
Vol 40 (4) ◽  
pp. 414-417 ◽  
Author(s):  
Kazuyuki Yano
Keyword(s):  
Substituent Effects ◽  
Methyl Substituent ◽  
Carbonium Ion

The Thermal Decomposition of N-Arylcarbamates of t-Alcohols. 2. Effects of Solvent, Temperature, and Substituents

1972 ◽  
Vol 50 (21) ◽  
pp. 3478-3487 ◽  
Author(s):  
S. J. Ashcroft ◽  
Melanie P. Thorne
Keyword(s):  
Diphenyl Ether ◽  
Substituent Effects ◽  
Reaction Rates ◽  
Specific Rate ◽  
Cyclic Transition ◽  
Tertiary Alcohols ◽  
Carbonium Ion ◽  
Tertiary Carbon ◽  
Cyclic Transition State ◽  
Influence Of Solvent

The influence of solvent, ring substituents, and tertiary carbon atom substituents on the decomposition at 423–473 K of some N-arylcarbamates of tertiary alcohols (p-XC6H4NHCO2C(CH3)2R, where X = CH3, H, Cl, NO2, R=C≡CH, C2H5, CH=CH2) has been investigated. In dodecane, diphenyl ether, acetophenone, nitrobenzene, and decanol, the reactions were first order yielding chiefly carbon dioxide, amine, and olefin. t-Pentyl carbamates yielded the olefins 2-methyl-1-butene and 2-methyl-2-butene in a 3:1 mixture. Solvent effects are reflected in variations in enthalpies and entropies of activation, but effects on the actual values of the specific rate constants are small. Substituent effects are also small, with changes in R from C≡CH to CH=CH2 producing only a tenfold rate increase. Variations in X yield Hammett σρ plots with slopes of about 0.50. These results are consistent with the charge separated cyclic transition state proposed before (1). In ethylene glycol, increased reaction rates and 1:1 yields of the olefins from the t-pentyl carbamates indicate a mechanism with greater carbonium ion character.

Methyl substituent effects for methyltryptophans in13C nmr

1992 ◽  
Vol 29 (5) ◽  
pp. 1181-1187 ◽  
Author(s):  
Minsu Lee ◽  
Robert S. Phillips
Keyword(s):  
Substituent Effects ◽  
Methyl Substituent
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