lecture 14 F08 given - Critically Important Announcement!...

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Critically Important Announcement! Exam 7 pm Thursday Night: Last Name Ends in Letter A-M, Go to Wel 2.224 Last Name Ends in Letter N-Z, Go to UTC 2.102A Dr. Sessler’s Office Hours will be in Welch 5.330 today (1:15 - 3:00 pm)
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Organic Chemistry I 310/318M Pre-Health Professionals Unique numbers: 54410, 54435, 54440, 54445, and 54655 Prof. Jonathan L. Sessler Lecture 14 Notes: Homework 3 due Wednesday. Exam 1 is Thurs evening; it will cover chapts. 1-3, inclusive; it will be in 2 rooms. Recitation will go an extra 30 minutes (until 6:30 pm tonight; Wel 1.308). Also, Candace will arrive at the recitation 30 minutes early on Tuesday night. Dr. Sessler’s Office Hours will be in Welch 5.330 today (1:15 - 3:00 pm) and Wednesday (usual 1:30-3:15 pm time).
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Fischer Projections • Another way to draw tetrahedral carbon atoms in 2-D – The molecule is drawn in the form of a cross. – The tetrahedral carbon is in the plane of the paper at the center of the cross. – Atoms connected to the tetrahedral carbon by horizontal bonds are behind the plane of the paper. – Atoms connected to the tetrahedral carbon by vertical bonds are in front of the plane of the paper.
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Up and down are both back away from you. Right and left are both up and at you. Rotating a Fischer projection formula by 90 o converts the structure into that of the enantiomer of the molecule originally represented. Rotating a Fischer projection formula by 180 o keeps the same enantiomer. Fischer Projections
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Fischer Projection: Substituent Exchange To compare a Fischer projection to another in a different orientation in order to see if they represent the same enantiomer: •Exchange any two substituents. This turns the molecule into its mirror image. •Exchange another two substituents. This then turns the molecule back into the original enantiomer. •Using a series of exchanges, convert one Fisher formula into the other. •If an odd number of exchanges are required, the two projection formulas represent different enantiomers. •If an even number of exchanges are required, the two projection formulas represent the same enantiomer.
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Fischer Projections - Absolute Configuration •Draw any correct Fischer projection formula of a chiral center. •Assign priorities to all of the substituents. •Using two consecutive substituent exchanges (to preserve the chirality of the Fischer formula), place group d (lowest priority) on the top. •If the a,b,c groups are now arranged in a clockwise order, the enantiomer is R: if in a counterclockwise order, the enantiomer is S.
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Enantiomers & Diastereomers • For a molecule with 1 chiral center, 2 1 = 2 stereoisomers are possible. • For a molecule with 2 chiral centers, a maximum of 2 2 = 4 stereoisomers are possible. • For a molecule with n chiral centers, a maximum of 2 n stereoisomers are possible.
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Enantiomers & Diastereomers • 2,3,4-Trihydroxybutanal – two chiral centers.
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This note was uploaded on 03/23/2010 for the course CH 54410 taught by Professor Sessler during the Spring '10 term at University of Texas at Austin.

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lecture 14 F08 given - Critically Important Announcement!...

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