Relations between Activation Energy, Rate of Reaction, Bond Dissociation Energy, and Heats of Formation, Atomization, and Reaction for the Substituted Methanes

1952 ◽  
Vol 20 (3) ◽  
pp. 524-524 ◽  
Author(s):  
H. J. Bernstein
Keyword(s):  
Activation Energy ◽  
Bond Dissociation Energy ◽  
Dissociation Energy ◽  
Heats Of Formation ◽  
Energy Rate ◽  
Bond Dissociation ◽  
Rate Of Reaction

Gas phase heats of formation of alkyl immonium ions

1981 ◽  
Vol 59 (14) ◽  
pp. 2228-2231 ◽  
Author(s):  
F. P. Lossing ◽  
Yai-Tai Lam ◽  
Allan Maccoll
Keyword(s):  
Electron Beam ◽  
Gas Phase ◽  
Bond Dissociation Energy ◽  
Dissociation Energy ◽  
Heats Of Formation ◽  
Canonical Forms ◽  
Bond Dissociation ◽  
Immonium Ions

Using an energy-resolved electron beam, the gas-phase heats of formation of [CH2NH2]+, [CH3CHNH2]+, [CH3NHCH2]+, [(CH3)2CNH2]+, [(CH3)2NCH2]+, [CH3CHNHCH3]+, [CH3CH2NHCH2]+, and [CH3CH2CHNH2]+ ions have been measured from their appearance energies in ionic dissociations. All of these ions can have a quaternary immonium structure as one of the canonical forms and are consequently more stable than other isomers. Introduction of the —NH2 group into a CH3+ ion brings about a decrease of over 4 eV in the heterolytic bond dissociation energy D(R+—H−), with slightly larger decreases for —NHR and —NR2 groups.

The C—Br bond dissociation energy in halogenated bromomethanes

1951 ◽  
Vol 209 (1096) ◽  
pp. 110-131 ◽  
Keyword(s):  
Bond Dissociation Energy ◽  
Dissociation Energy ◽  
Methyl Bromide ◽  
Frequency Factor ◽  
Unimolecular Dissociation ◽  
Bond Dissociation Energies ◽  
Kcal Mole ◽  
Fast Reaction ◽  
Bond Dissociation ◽  
Dissociation Energies

The pyrolyses of methyl bromide and of the halogenated bromomethanes, CH 2 CI. Br, CH 2 Br 2 , CHCl 2 .Br, CHBr 3 , CF 3 Br, CCI 3 . Br and CBr 4 , have been investigated by the ‘toluene-carrier' technique. It has been shown that all these decompositions were initiated by the unimolecular process R Br → R + Br. (1) Since all these decompositions were carried out in the presence of an excess of toluene, the bromine atoms produced in process (1) were readily removed by the fast reaction C 6 H 5 .CH 3 + Br → C 6 H 5 . CH 2 • + HBr. Hence, the rate of the unimolecular process (1) has been measured by the rate of formation of HBr. The C—Br bond dissociation energies were assumed to be equal to the activation energies of the relevant unimolecular dissociation processes. These were calculated by using the expression k ═ 2 x 10 13 exp (- D/RT ). The reason for choosing this particular value of 2 x 10 13 sec. -1 for the frequency factor of these reactions is discussed. The values obtained for the C—Br bond dissociation energies in the investigated bromomethanes are: D (C—Br) D (C—Br) compound (kcal./mole) compound (kcal./mole) CH 3 Br (67.5) CHBr 3 55.5 CH 2 CIBr 61.0 CF 3 Br 64.5 CH 2 Br 2 62.5 CCI 3 Br 49.0 CHCl 2 Br 53.5 CBr 4 49.0 The possible factors responsible for the variation of the C—Br bond dissociation energy in these compounds have been pointed out.

Sign in / Sign up

Export Citation Format

Share Document