41809-44-3Relevant academic research and scientific papers
Thermolysis of Geminal Bisazoalkanes. Stabilization of a Carbon-Centered Radical by the Azo Substituent
Engel, Paul S.,Wang, Chengrong,Chen, Yan-Qiu,He, Shu-Lin,Andrews, B. Kim,Weisman, R. Bruce
, p. 6257 - 6261 (1994)
Two geminal bisazoalkanes (1 and 2) have been employed to generate a radical center next to the azo group.The 8.0 kcal/mol lower ΔG(excit.) for thermolysis of 1 and 2 relative to model compounds 6 and 7 is dissected into a 1 kcal/mol contribution from ground state elevation of 1 and 2 and at least 2.6 kcal/mol from phenyl stabilization of radical 3.Any extra stabilization of the aliphatic 2,3-diazaallyl radical (4) relative to α,α-dimethylallyl amounts to no more than 4.4 kcal/mol.Finally, γ-phenyl conjugation of the α,α-dimethylallyl radical stabilizes it by 4.5 kcal/mol.
Quantification of the electrophilicities of diazonium ions
Mayr, Herbert,Hartnagel, Manfred,Grimm, Klaus
, p. 55 - 69 (2007/10/03)
The kinetics of the reactions of arenediazonium ions with arenes, alkenes, allylsilanes, allylstannanes, and silyl ketene acetals have been studied in acetonitrile solution. The reactions follow second-order kinetics, and in several cases rate-determining attack of the diazonium ion has been proven by kinetic isotope effect studies (1a + 2b), by the independence of the allylsilane reactivities of the rate of desilylation (1a + 10a, d) and by the independence of the rate constants of the diazonium counterion. A decrease of the rate constant with increasing solvent donor ability (correlation with Gutmann's donor number) was found. The reactions of diazonium ions with π-nucleophiles roughly follow the correlation lgk (20°C) = s (E + N), previously derived for the reactions of carbocations with nucleophiles. With the E parameters derived for diazonium ions, rate constants for azo couplings with aromatic and nonaromatic π-nucleophiles can be predicted with an accuracy of ≈102. On the basis of E, the electrophilic reactivities of diazonium ions can be compared with those of carbocations (Figure 9), and the combination with the nucleophilicity parameters N (Figure 10) gives a first clue on possible azo coupling reactions. Literature reports are discussed within this scheme. VCH Verlagsgesellschaft mbH, 1997.
