Portmess Homework Q&S 88

Portmess Homework Q&S 88 - 82 ALCOHOLS AND ALKYL...

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Unformatted text preview: 82 ALCOHOLS AND ALKYL HALIDES need to complete the equation by realizing that HF is also formed in the fluorination of alkanes. The balanced equation is therefore: (CH3)4C 4.39 (CF3)4C 12F2 12HF The reaction is free-radical chlorination, and substitution occurs at all possible positions that bear a replaceable hydrogen. Write the structure of the starting material, and identify the nonequivalent hydrogens. F C C F Cl Cl H CH3 1,2-Dichloro-1,1-difluoropropane The problem states that one of the products is 1,2,3-trichloro-1,1-difluoropropane. This compound arises by substitution of one of the methyl hydrogens by chlorine. We are told that the other product is an isomer of 1,2,3-trichloro-1,1-difluoropropane; therefore, it must be formed by replacement of the hydrogen at C-2. F C C F Cl Cl F H Cl 1,2,3-Trichloro-1,1-difluoropropane 4.40 C C F CH2Cl Cl Cl CH3 1,2,2-Trichloro-1,1-difluoropropane Free-radical chlorination leads to substitution at each carbon that bears a hydrogen. This problem essentially requires you to recognize structures that possess various numbers of nonequivalent hydrogens. The easiest way to determine the number of constitutional isomers that can be formed by chlorination of a particular compound is to replace one hydrogen with chlorine and assign an IUPAC name to the product. Continue by replacing one hydrogen on each carbon in the compound, and compare names to identify duplicates. (a) 2,2-Dimethylpropane is the C5H12 isomer that gives a single monochloride, since all the hydrogens are equivalent. CH3 CH3 CH3CCH3 Cl2 CH3CCH2Cl light CH3 CH3 2,2-Dimethylpropane (b) 1-Chloro-2,2-dimethylpropane The C5H12 isomer that has three nonequivalent sets of hydrogens is pentane. It yields three isomeric monochlorides on free-radical chlorination. ClCH2CH2CH2CH2CH3 1-Chloropentane CH3CH2CH2CH2CH3 Cl2 CH3CHCH2CH2CH3 Pentane Cl 2-Chloropentane CH3CH2CHCH2CH3 Cl 3-Chloropentane Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website ...
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This note was uploaded on 09/20/2011 for the course CHM 2210 taught by Professor Reynolds during the Spring '01 term at University of Florida.

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