L18a - Rotation consequences HO Section 7.16 conc H2SO4...

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1 1 1. dehydration 2. electrophilic addition 3. dehydrohalogenation 4. shifting (rearrangement) HO conc H 2 SO 4 heat dehydration elect r ophi . dehyd oh. s h i f t in g ( r.. 1% 93% 1% 6% Whenever a carbocation intermediate is involved in a reaction, for what do you always have to watch out? 5 bonds?!! You MUST think through the mechanism. 2 Rotation 1 2 3 4 5 6 2% 0% 0% 0% 2% 95% 1. 1 2. 2 3. 3 4. 4 5. 5 6. 6 © Kay Sandberg Section 7.16 Rotation consequences CH 3 CH 3 CH 3 H Cl Br LL If you rotate the Fischer projection by 180 degrees in the plane of the screen, where will the Br end up and with what bond characteristic? 1) UL wedge bond 2) UL dashed bond 3) UR wedge bond 4) UR dashed bond 5) LR wedge bond 6) LR dashed bond The Br is in the lower left (LL) corner of this Fischer projection. 3 © Kay Sandberg Section 7.16 Rotation consequences CH 3 CH 3 CH 3 H Cl Br CH 3 CH 3 Br Cl H H 3 C LL UR CH 3 CH 3 Br H CH 3 Cl CH 3 CH 3 CH 3 Cl Br H 4 CH 3 CH 3 CH 3 H Cl Br © Kay Sandberg Section 7.16 Rotation consequences CH 3 CH 3 H 3 CH Cl Br wedges become dashes CH 3 CH 3 Br H CH 3 Cl CH 3 CH 3 Cl H 3 C H Br Rotate by 180 degrees 5 © Kay Sandberg Section 7.16 CH 3 Cl H 3 H 3 CB r Green Blue CH 3 CH 3 HC H 3 Br Cl CH 3 CH 3 Br Cl H H 3 C If a molecule has only 1 chirality center, then the molecule is chiral which means it’s mirror imagine will be it’s enantiomer. * S CH 3 CH 3 Br Cl H 3 R * Rotate the entire molecule Rotate about carbon Isomeric relationship? 6 ©Dr. Kay Sandberg Last lecture This lecture Chirality chiral molecules containing more than one chirality center. reactions that create stereoisomers S N 2 enantiomers (racemic product mixture) meso-form product (achiral) diastereomer product mixture
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2 7 2 3 CH 3 OH H CH 3 H OH © Kay Sandberg Section 7.3 If a molecule contains a plane of symmetry then the molecule is achiral H 3 C HO H OH H CH 3 meso - 2,3-butanediol achiral S R mirror plane (2S,3R)-2,3-butanediol (2R,3S)-2,3-butanediol 2 3 CH 3 HO H CH 3 H HO 8 © Kay Sandberg Note: If a molecule has: 1 chirality center more than 1 chirality center may or may not be chiral Is it a meso -form? 9 © Kay Sandberg H 3 C H 2 N H HO H CH 3 Section 7.10 ( )-3-amino-2-butanol (2 R, 3 R )-3-amino-2-butanol liquid Solid, mp 49 o C 2 _, 3 _ 1 2 3 4 2 R, 3 S H 3 C H NH 2 HO H CH 3 amino group 10 Configure 1 2 3 4 1% 2% 1% 96% 1. 1 2. 2 3. 3 4. 4 1 3 4 5 H H 3 C HO H H CH 3 H H 3 C HO H CH 3 H CH 3 H HO H CH 3 H © Kay Sandberg Section 7.12 CH 3 H HO H H CH 3 (2 _, 3 _ )- (2 _, 3 _ )- (2 _, 3 _ )- (2 _, 3 _ )- 3-penten-2-ol Enantiomers enantiomers dia dia (2 _, 3 _ )- (2 R, 3 E S, 3 Z )?? S, 3 Z )- E )- 1: (2 ,3 E ) 2: (2 ,3 Z ) 3: (2 ,3 ) 4: (2 ,3 ) 11 © Kay Sandberg Section 7.9 Rxns that create a stereogenic center C C H H H 3 C H CH 3 CO 2 OH (peroxyacetic acid) Epoxidation O 12 C C H H H H 3 C O © Kay Sandberg Section 7.9 Rxns that create a stereogenic center +c h i r a l C C H H H H 3 C * C C H H H H 3 C O * ( R )-1,2-epoxypropane ( S )-1,2-epoxypropane O O H O O O H O 50% 50% prochiral enantiotopic enantiotopic faces enantiomers enantiomers
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3 13 C C H H H H 3 C O C C H H H H 3 C O © Kay Sandberg Section 7.9 Rxns that create a stereogenic center C C H H H 3 C H CH 3 CO 2 OH
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This note was uploaded on 03/30/2009 for the course CH ORGANIC CH taught by Professor Kaysandberg during the Spring '09 term at N.C. State.

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L18a - Rotation consequences HO Section 7.16 conc H2SO4...

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