Specific Solvation of Polar Transition States

1964 ◽  
Vol 68 (2) ◽  
pp. 215-219 ◽  
Author(s):  
R. F. Hudson
Keyword(s):  
Transition States ◽  
Specific Solvation ◽  
Polar Transition

The thermal decomposition of trimethylacetyl bromide

1970 ◽  
Vol 23 (3) ◽  
pp. 525 ◽  
Author(s):  
BS Lennon ◽  
VR Stimson
Keyword(s):  
Thermal Decomposition ◽  
Carbon Monoxide ◽  
Hydrogen Bromide ◽  
Transition States ◽  
Volume Ratio ◽  
Reaction Vessel ◽  
Chain Mechanism ◽  
Radical Chain ◽  
First Order ◽  
Polar Transition

Trimethylacetyl bromide decomposes at 298-364� into isobutene, carbon monoxide, and hydrogen bromide in a first-order manner with rate given by k1 = 138 x 1014exp(-48920/RT) sec-1 The rate is unaffected by addition of the products or of inhibitors, or by increase of the surface/volume ratio of the reaction vessel. The likely radical chain mechanism is considered and rejected. The reaction is believed to be a molecular one, and possible cyclic and polar transition states are discussed.

Solvolysis of 4-Halogeno-4-Alkyl-2,6-di-tert-butylcyclohexa-2,5-dienones Induced by Positive Halogen Donors as Electrophiles

2013 ◽  
Vol 66 (11) ◽  
pp. 1386 ◽  
Author(s):  
Kanji Omura
Keyword(s):  
Hydrogen Bond ◽  
Halogen Atom ◽  
Aprotic Solvent ◽  
Transition States ◽  
Solvent System ◽  
Solvent Mixture ◽  
Electrophilic Attack ◽  
Polar Aprotic Solvent ◽  
Polar Transition ◽  
Rate Limiting

Positive halogen donors such as N-iodosuccinimide (NIS) induce solvolysis of dienones 1, as model 4-halogenocyclohexa-2,5-dienones, in different hydroxylic solvents (ROH), yielding the 4-RO-cyclohexa-2,5-dienones (2). The rate of the solvolysis with NIS is highly dependent on the structure of ROH. The problem of such dependency is overcome by running the reaction in ROH diluted with MeCN, a polar aprotic solvent, in place of pure ROH; the rate of the reaction in the ROH-MeCN solvent mixture is almost independent of the structure (or the polarity) of ROH, and the reaction is completed faster or markedly faster than in neat ROH. The results suggest that the solvolysis rate is controlled by the polarity of the solvent system, although the hydrogen-bond acceptability of MeCN for dilution also accelerates the reaction. A mechanism for the solvolysis is proposed, involving electrophilic attack of a positive halogen donor at the halogen atom of 1, generating the 4-oxocyclohexa-2,5-dienyl cation intermediates (8) via the rate-limiting polar transition states.

Photochemical .alpha. cleavage of benzoin derivatives. Polar transition states for free-radical formation

1975 ◽  
Vol 97 (6) ◽  
pp. 1519-1525 ◽  
Author(s):  
F. D. Lewis ◽  
R. T. Lauterbach ◽  
H. G. Heine ◽  
W. Hartmann ◽  
H. Rudolph
Keyword(s):  
Free Radical ◽  
Transition States ◽  
Radical Formation ◽  
Polar Transition ◽  
Free Radical Formation

The reality of polar transition states of photobromination of toluenes by N-bromosuccinimide (NBS)

1985 ◽  
Vol 107 (14) ◽  
pp. 4234-4237 ◽  
Author(s):  
Sung Soo Kim ◽  
Seung Yong Choi ◽  
Chul Hyun Kang
Keyword(s):  
Transition States ◽  
Polar Transition
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