Butanols enantiomers

Figure 5.3 (a) Three-dimensional drawings of the 2-butanol enantiomers I and II. 

PA = 226 kcal moP ), the predominant formation (6.4 to 1) of the (7 ,5 )-di-2-butyl ether over the (R,R) and (5, 5 )-forms is attributed to a simple backside displacement in the proton-bound adduct of the starting 2-butanol enantiomer with inversion of configuration of the reaction site and loss of a molecule of water. When tri-n-propylamine is replaced by the less basic NH3 (PA = 196 kcal moF ), fast neutralization of the proton-bound dimers of the starting 2-butanol is prevented and, therefore, they can grow, producing aggregates that resemble solution microenvironments in which SnI pathways may be accessible as well. In them or in their primary substituted derivatives, consecutive nucleophilic displacements may take place. As a consequence, the stereospecificity of the process is lost and the [(R,S)-di-2-butyl ether]/[(7 ,7 )- and (5, 5 )-di-2-butyl ethers] ratio falls down to 1.2. In this case. 

FIGURE 5.3 (a) Three-dimensional drawings of the 2-butanol enantiomers I and II. (b) Models of the 2-butanol enantiomers, (c) An unsuccessful attempt to superpose models of I and II. 

We can illustrate the application of the rule with the following 2-butanol enantiomer ... 

Many of these properties (e.g., boiling points, melting points, and solubilities) are dependent on the magnitude of the intermolecular forces operating between the molecules (Section 2.13), and for molecules that are mirror images of each other these forces will be identical. We can see an example of this if we examine Table 5.1, where boiling points of the 2-butanol enantiomers are listed. 

Let us suppose, for example, that a mixture of the 2-butanol enantiomers showed a specific rotation of +6.76. We would then say that the enantiomeric excess of the (5)-(+)-2-butanol is 50% ... 

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