Ch_322a_11.014

Ch_322a_11.014 - A similar reaction occurs with primary and...

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Alkyl Halides from the Reaction of Alcohols with PBr 3 or SOCl 2 Phosphorous Tribromide A general synthesis of alkyl bromides is the reaction of alcohols with PBr 3 (a colorless, fuming liquid, bp 173 o C). An advantage of this procedure is the absence of carbocation rearrangements. (1) R-O H : : + P-Br Br Br R-O H PBr 2 + + Br - (2) R-O H PBr 2 + Br - + good leaving group R-Br + HOPBr 2 alkyl bromide S N 2 : : This reaction proceeds well with primary and secondary alcohols. The overall stoichiometry is: 3 ROH + PBr 3 3 RBr + 3 H 3 PO 3 phosphorous acid
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Thionyl Chloride
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Unformatted text preview: A similar reaction occurs with primary and secondary alcohols and SOCl 2 to yield alkyl chlorides. (1) R-O H : : + Cl-S-Cl O = : : R-O H S-Cl Cl O : :-+ (-HCl) R-O-S-Cl O alkyl chlorosulfite (2) R-O-S-Cl O Cl :-+ R-Cl + O-S-Cl O-unstable SO 2 + Cl-Examples 3 CH 3 CHCH 2 CH 3 OH + PBr 3 2-butanol 3 CH 3 CHCH 2 CH 3 Br 2-bromobutane + H 3 PO 3 CH 3 CHCH 3 OH + SOCl 2 2-propanol CH 3 CHCH 3 Cl 2-chloropropane + SO 2 + HCl...
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This note was uploaded on 07/22/2009 for the course CHEM 322AL taught by Professor Jung during the Summer '07 term at USC.

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Ch_322a_11.014 - A similar reaction occurs with primary and...

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