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Week 7 Lab Presentation

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by

whitty li

on 21 May 2014

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Transcript of Week 7 Lab Presentation


Theory
Determining Absolute Configuration of a Secondary Alcohol Using TLC
Absolute Configuration Lab

By:
Whitty Li
Ashley Tran
Deryn Ongchangco

WEDNESDAY - 05.21.14
Theory
The catalyst is reacting with a chiral, secondary, aromatic alcohol to produce an ester.

In this competing method, one enantiomer will react with the alcohol faster than the other.

According to mnemonic…

Results
Reaction A:
Alcohol:3928.116
Ester: 6322.711
Reaction B:
Alcohol: 610.962
Ester: 11599.731

Reaction Conversion A:
6322.711/(6322.711+3928.116) =.6168 x 100 =
61.68%

Reaction Conversion for B: 11599.731/(11599.731+610.962) = .9947 X 100 =
99.47%




Mechanism
Alcohol + anhydride = ester
[+catalyst to speed up rxn]
Results
The CEC method involves reacting an unknown alcohol with each enantiomer of the catalyst: R-HBTM and S-HBTM.

Enzymes (catalysts) are sterospecific 3D molecules; chirality is key for a rxn b/c specific fit induces binding to substrate.

Enantiomers are mirror images of chiral centers. They are identical except in optical activity and interactions with other chiral centers.

Basis for Mnemonic
Specific pairing is due to sterics and proximity of functional groups.
Kinetic product

Theory - TLC Analysis
Density and Integration

Reaction Conversion = integration of ester / (integration of ester + integration of alcohol) x 100
How does density correlate with reaction rate??
Week 7
M. Kubota - 40804 - 51LC
Discussion
Unknown: 4-bromo-a-benzylmethyl alcohol
Faster Reaction: B
Catalyst of faster reaction: R-HBTM
Absolute configuration of unknown: S
Conclusion
Configuration of the HBTM catalyst and the unknown alcohol was determined by reacting them together and analyzing them with TLC.
- S-4-Bromo-α-methylbenzyl alcohol and R-HBTM

Complete reaction:
- Properly add in the reagents in a timely manner
- Allow for complete reaction (full hour)

Other techniques
- Gas chromatography
- NMR Spectroscopy
Catalyst Reaction +
Esterification
Full transcript