Methoxymethyl chloride, conformation

Let us consider selected data calculated ab initio (RHF/4-31G level) by Jeffrey and Yates (238) (Table 11). These are quite reliable data, in contrast to data generated by lower level semiempirical methods (9, 236, 237, 239), which do not reproduce the anomeric effect very well (57, 211, 238). The constants V for 122 and 123, responsible for dipole-dipole interactions, have opposite signs. This means that dipolar interactions favor the sp conformation of 123 but the ap conformation of 122. A negative Fj term for methoxymethyl chloride (122) should be considered abnormal since it does not agree with the expected (cf. 121 in Figure 20) most effective attractive interaction between C—Cl and CHj—O bond dipoles in the sp conformer of 122. 

Molecular orbital calculations (4-3IG) have found 4kcal as the difference between the two conformations shown below for methoxymethyl chloride. ... 

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