STEREOCHEMISTRY 159 The three highest ranking substituents trace a counterclockwise path when the lowest ranked lbstituent is held away from The absolute configuration is S, and thus the compound is(S)-(+)-1-bromo-2-methylbutane (d) The highest ranked substituent at the stereogenic center of 3-buten-2-ol is the hydroxyl group ind the lowest ranked substituent is H. Of the remaining two, vinyl outranks methy Order of precedence: HO> CH,CH>CH3>H The lowest ranking substituent(H) is directed away from you in the drawing. We see that the order of decreasing precedence appears in a counterclockwise manner. (+)-3-Buten-2-o1 The absolute configuration is S, and the compound is(S)-(+)-3-buten-2-o1 7.8 (b) The stereogenic center is the carbon that bears the methyl group Its substituents are -CF2CH2>-CH, CF2>CH3> H When the lowest ranked substituent points away from you, the remaining three must appe ty ding order of precedence in a counterclockwise fashion in the S difluoro-2-methylcyclopropane is therefore 7.9(b) The Fischer projection of(R)-(+)-1-fuoro-2-methylbutane is analogous to that of the alcohol in part(a). The only difference in the two is that fluorine has replaced hydroxyl as a sub stituent at C-1 H,F ChF is the same as which becomes the Fischer projection H--CH CH,CH CHCH CHCH Although other Fischer projections may be drawn by rotating the perspective view in other di rections, the one shown is preferred because it has the longest chain of carbon atoms oriented on the vertical axis with the lowest numbered carbon at the top (c) As in the previous parts of this problem, orient the structural formula of (S)-(+)-l-bromo- 2-methylbutane so the segment BrCH,C-CH,CH3 is aligned vertically with the lowest numbered carbon at the top. C-CH, Br is the same as H3C which becomes the Fischer projection HC-H CHa CH CH, CH3 CHCH Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE WebsiteThe three highest ranking substituents trace a counterclockwise path when the lowest ranked substituent is held away from you. The absolute configuration is S, and thus the compound is (S)-()-1-bromo-2-methylbutane. (d) The highest ranked substituent at the stereogenic center of 3-buten-2-ol is the hydroxyl group, and the lowest ranked substituent is H. Of the remaining two, vinyl outranks methyl. Order of precedence: HO  CH2?CH  CH3  H The lowest ranking substituent (H) is directed away from you in the drawing. We see that the order of decreasing precedence appears in a counterclockwise manner. The absolute configuration is S, and the compound is (S)-()-3-buten-2-ol. 7.8 (b) The stereogenic center is the carbon that bears the methyl group. Its substituents are: When the lowest ranked substituent points away from you, the remaining three must appear in descending order of precedence in a counterclockwise fashion in the S enantiomer. (S)-1, 1- difluoro-2-methylcyclopropane is therefore 7.9 (b) The Fischer projection of (R)-()-1-fluoro-2-methylbutane is analogous to that of the alcohol in part (a). The only difference in the two is that fluorine has replaced hydroxyl as a sub￾stituent at C-1. Although other Fischer projections may be drawn by rotating the perspective view in other di￾rections, the one shown is preferred because it has the longest chain of carbon atoms oriented on the vertical axis with the lowest numbered carbon at the top. (c) As in the previous parts of this problem, orient the structural formula of (S)-()-1-bromo- 2-methylbutane so the segment BrCH2@C@CH2CH3 is aligned vertically with the lowest numbered carbon at the top. C CH3 CH3CH2 CH2Br H H3C C CH2CH3 CH2Br H H3C CH2CH3 CH2Br is the same as which becomes the Fischer projection H C H3C CH3CH2 CH2F H C CH3 CH2CH3 CH2F H CH3 CH2CH3 CH2F is the same as which becomes the Fischer projection H H CH3 F F CF2CH2  CH2CF2  CH3  H Highest rank Lowest rank ()-3-Buten-2-ol CH2 CH2 HO C H H3C CH2 C H3C CH OH C BrCH2 CH3 CH2CH3 STEREOCHEMISTRY 159 Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website