Electronically from halogen atom reactions

Electronically excited halogen atoms (2P1/2) have been observed as products from the reactions... 

The thermochemistry and results summarized in Table 2.3 are based upon the assumption that only ground electronic state halogen atoms are involved as reactants and products. The energy difference between the upper ( A/2) and lower ( 3/2) spin orbit states are 1.2, 2.5, 10.5, and 21.7 kcal mole for the halogen series. For room temperature equilibrium conditions, only F( Pi/2) can affect the reactant side of the equation. According to theoretical considerations, 2 1,2 should react more slowly than the Pzi2 state. Simple correlation diagrams, show that the X( Fi/2) state correlates with the X ( Fi/2) product state in X -I- HX reactions. The possibility that /( Fi/2) is a product from the Br, Cl, and F + HI reactions has been excluded by direct tests for /( Fi/2 — 7 3/2) emission. In contrast,... 

Perhaloalkanes have been found to scramble halogen atoms via consecutive halophilic reactions following carbanion generation by halophilic attack by base. S l reaction of an allylsilane has been applied in a stereocontrolled synthesis of ( )-dihydronepetalactone, and functionalized aryl and arylmethyl carbanions have been generated by reductive cleavage of aryl and arylmethyl alkyl ethers by electron transfer from alkali metals. ... 

Electrochemical oxidation of alkyl bromides and iodides leads to loss of a nonbonding electron from the halogen substituent, followed by cleavage of the carbon-halogen bond to form a carbonium ion and a halogen atom. The products isolated are formed by further reactions of the carbonium ion while two of the halogen at-... 

Insertion reactions of silylene into a number of single bonds have been observed. The bonds include Si—O, Si N, Si H, Si halogen, strained C O, Si Si, O—H, N—H, and C—H (intramolecular only). Insertion into an X H bond can be initiated by the formation of silaylide (50) with the donation of a pair of electrons from a heteroatom X to form a bond to a divalent sihcon atom (Scheme 14.26). 

To observe the kinetic effect of the chemical reaction of an electronically excited atom, the rate must be significantly different from that of the ground state atom, as spin orbit relaxation may compete with reaction. The separation of these processes is inherent in studies of the reactions of excited halogen atoms. Clearly, where a strong attractive potential facilitates chemical reaction, this chemical interaction will also aid spin orbit relaxation itself (Section VII). Thus relatively strongly endothermic, slow, chemical reaction... 

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