2- Chloropropane chirality

Indicate which of the following molecules are optical isomers and identify the chiral carbon atoms in those that are (a) CH,CHBrCH2CH3 (b) CH3CH2CHCl2 (c) l-bromo-2-chloropropane (d) 1,2-dichloropentane. 

Ab initio STO-3G calculationswere performed on the supermolecules formed by a nucleophile and a chiral substrate (2-chloropropanal or 2-methylbutanal). The nucleophile, simulated by H , is located at 1.5 A from the carbon atom, in a direction perpendicular to the carbonyl axis. Hence, to each reaction correspond two diastereoisomeric supermolecules resulting from attack on one face or the other of the 7T system. These molecules are thus models of the diastereoisomeric transition states. In Fig Ill and IV, their relative energies are plotted as a function of their conformations. The solid (dashed) lines correspond to the transition states of type 5... 

A new and efficient one-pot approach towards chiral 2-azetidinones has been reported to start from (25)-chloro-l-propanol. The treatment of this latter with 5 equivalents of pyridinium chlorochromate in dichloromethane at room temperature afforded the (2S)-chloropropanal which treated with 1 equivalent of amine and 1.5 equivalents of MgSC>4 yielded the (S)-N-(2-chloropropvIiclene)amines. Finally,... 

FIGURE 5.8 (a) 2-Chloropropane has a plane of symmetry and is achiral, (b) 2-Chlorobutane does not possess a plane of symmetry and is chiral. 

What is it about their structures that leads to chirality in 2-chlorobutane but not in 2-chloropropane Notice that, in 2-chlorobutane, carbon atom 2, the one marked with an asterisk, has four different groups attached to it (Cl, H, CH3, and CH2CH3). A carbon atom with four different groups attached to it is called a stereogenic carbon atom. This type of carbon is also called a stereogenic center because it gives rise to stereoisomers. 

CPD and 2,3-DCP are chiral compounds, which occur in protein hydrolysates and foods as racemic mixtines of corresponding enantiomers (-)-(J )-3-chloropropane-l,2-diol (12-28), (-F)-(S)-3-chloropropane-l,2-diol (12-29), (i )-2,3-dichloropropan-l-ol (12-30) and (S)-2,3-dichloropropan-l-ol (12-31), respectively. 

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