CHEM+241+Extra+Credit+Sid+Joshi

Siddharth Joshi CHEM 241 – Extra Credit Assignment Professor Bradley []
 * Self-Discrimination of Enantiomers in Hydrogen-Bonded Dimers**

In the above article, the stability of homochiral and heterochiral hydrogen-bonded dimers of a set of small α-amino alcohols was studied. Some model compounds from the study are show in Figure 1.

**Figure 1.** Schematic example of monomers considered. //__Basic questions posed, which are answered by the article__//: How is the length of hydrogen-bonds related to the molecular configuration of each of the dimers? Are heterochiral alcoholic dimers more stable than homochiral dimers? For the nonchiral α-amino alcohol molecules considered, are the chair or boat configurations better for molecular stability?

//__The important points/answers to take away from this paper__//: **Figure 2**. Representation of Hydrogen-bond distance compared to interaction energy for dimers of X/Y = H/CH3 and CF3 and CH3 (circles & squares respectively)
 * We can state that if the two molecules in a hydrogen-bonded dimer have the same chirality, then the molecule is homochiral. However, if the two molecules in a hydrogen-bonded dimer have opposite chirality, then it can be called heterochiral.
 * For all cases__, the shortest hydrogen-bonds corresponded to the configuration with the lowest relative energy.__
 * __In the complexes of nonchiral monomers, the chair configuration is more stable than the boat configuration by a small margin__. These energetic differences increase as the size of the X group (pictured in Figure 1) increases; 0.55, 0.90, 1.02 and 2.34 kCal/mol for H, F, CH3 and CF3 respectively.
 * __In chiral systems, the most favorable energetically stable dimers obtained are heterochiral in chair configuration__, while the worst are homochiral in a boat configuration. The maximum difference between these two extreme configurations being 4 kCal/mol.
 * Two figures showing the lowest energy conformation for homochiral (Figure 3) and heterochiral (Figure 4) molecules are drawn below.


 * Figure 3**. Lowest Energy Homochiral Conformation **Figure 4**. Lowest Energy Heterochiral Conformation

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