Solutions_Manual_for_Organic_Chemistry_6th_Ed 80

Solutions_Manual_for_Organic_Chemistry_6th_Ed 80 - 4-44 (...

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Unformatted text preview: 4-44 ( a) CH2=CH-CH2 . ..... f----l.� .. ( c) ( d) CH3 -C-O· •• :0: II .. .� ..f----l ... CH3-C=O •• :0: I . 4 -45 (a) Mechanism initiation O I H H H ..f----l.� .. ... �H UH --- H (e) �H U H H f----l.� ....... Br- B r nn cY · H H H hv 2 B r· p ropagation H3C � CH3 H � '=Jj.J � _ JH3C yy' CH3 � -1 The 3 ° allylic H is abstracted selecti vely (faster t han any other type In the molecule) , fonrung an intermedi ate represented by two non-equivalent resonance forms. Parti al radic al c h aracter on two different carbons of the allylic radical leads to two different product s . WId·) Br + HBr _ � j � H3C� CH3 W W l f second propagation step + B r· (b) There are two reasons why the H s hown i s the one that is abstracted by bromine radical: the H i s 3° and it is allylic, that i s , neighbori n g a double bond. Both of these factors stabi l i ze the radical that is created by removing the H a tom. 4-46 Where mixtures are possible, only the major product is shown . (a) 0 I I � � ( b) ( c) � CH� U CH3H C H3 -C-C-CH3 CH3 C H3 � rY B r V o nly one product possible 3 ° hydrogen abstracted selecti vely, faster than 2° or 1 ° I - I CH3 B r CH3-C-C-CH3 CH3 CH3 I I I I 3 ° hydrogen abstracted selectively, faster than 1 ° 72 ...
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