1559T_ch11_199-21911/02/0521:43Pa9e212 ⊕ EQA 212 Chapter 11 ALKENES;INFRARED SPECTROSCOPY AND MASS SPECTROMETRY stercochemistry of the two chiral carbons in the haloalkane. 49.The more hindered (CH)COK will favor removal of protons toward the less crowded"ends"of molecules.thus giving less stable products.Ethoxide eliminations will favor more stable products. NaOCH-CH CHSCH-OH auine mr CH)cOKCH.cou (a)CH.OCH.CH. (b)CH.CH.CH.CH.CH:OCH.CH CH.CH.CH.CH.CH.Br +1-pentenc (c)trans-and cis-2-pentenes CH.CH.CH.CHBrCH, 1-Pentene CH CH CI (d) H CH rafa CH-CH2 O (f) CH.CH CH、H CH.CH.CH.CH.CH CH H CH.CH-CH, CH.CH.CH (h) H、CH cH,CH、QHCH,QH CH:CH2 CHCH.CH, H十CH,CH CH.CH2CH A haloalkane of general structure RRCHOCHXOR will have only one conformation with H anti to X. Therefore, only a single alkene stereoisomer can form. Its stereochemistry will be determined by the stereochemistry of the two chiral carbons in the haloalkane. 49. The more hindered (CH3)3CO K will favor removal of protons toward the less crowded “ends” of molecules, thus giving less stable products. Ethoxide eliminations will favor more stable products. Product with Structure of Product with NaOCH2CH3 in CH3CH2OH starting material (CH3)3COK in (CH3)3COH (a) CH3OCH2CH3 CH3Cl CH3OC(CH3)3 (b) CH3CH2CH2CH2CH2OCH2CH3 CH3CH2CH2CH2CH2Br 1-Pentene  1-pentene (c) trans- and cis-2-pentenes CH3CH2CH2CHBrCH3 1-Pentene (d) (e) (f ) (g) (h) CH (R) CH2 CH2CH3 CH2CH2CH3 H CH3 CH3CH2 CH2CH2CH3 Cl H H CH3 H CH2CH2CH3 CH2CH3 Cl H (Z) C H C CH3 CH3CH2 CH2CH2CH3 CH (S) CH2 CH3CH2 CH2CH2CH3 H CH3 CH3CH2CH2 CH2CH3 Cl H H CH3 H CH2CH2CH3 CH3CH2 Cl H (Z) C H C CH3 CH3CH2CH2 CH2CH3 CH (R) CH2 CH2CH3 CH2CH2CH3 H CH3 CH3CH2 CH2CH2CH3 Cl H H CH3 H CH2CH2CH3 CH2CH3 Cl H (E) C H C CH3 CH3CH2 CH2CH2CH3 CH CH2 CH3 CH CH Br H 3 CH3 CH3 Cl CH2 212 • Chapter 11 ALKENES; INFRARED SPECTROSCOPY AND MASS SPECTROMETRY 1559T_ch11_199-219 11/02/05 21:43 Page 212