Photogeneration of carbocations: applications in physical organic chemistry and the design of suitable precursors

Autor:	Herbert Mayr, Johannes Ammer
Rok vydání:	2013
Předmět:	chemistry.chemical_classification Aryl Organic Chemistry Carbocation Photochemistry chemistry.chemical_compound Microsecond Nucleophile chemistry Physical organic chemistry Flash photolysis Phosphonium Physical and Theoretical Chemistry Alkyl
Zdroj:	Journal of Physical Organic Chemistry. 26:956-969
ISSN:	0894-3230
DOI:	10.1002/poc.3132
Popis:	The generation of carbocations by laser flash photolysis of suitable precursors provides information about their reactivities toward nucleophiles on the nanosecond and microsecond time scale that cannot be obtained by conventional methods. We discuss the requirements that must be met by the precursors to achieve sufficient yields of the carbocations under the conditions of kinetic experiments. These include (i) efficient photogeneration of the carbocations; (ii) the stability of the precursor in the sample solution; (iii) the absorption of the precursor at the excitation wavelength; and (iv) sufficient lifetimes of the photogenerated carbocations for the observation of their reactivities toward the nucleophiles of interest. We provide an overview of the advantages and disadvantages of some precursors that are commonly employed for the generation of carbocations R+. This includes alkyl halides R–Cl, acetates R–OAc, aryl ethers R–OAr, ammonium salts R–NR′3+, and phosphonium salts R–PR′3+. Copyright © 2013 John Wiley & Sons, Ltd.
Databáze:	OpenAIRE
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