Influence of gamma-hydrogens (hydrogens three bonds away) in calculating C-13 chemical shifts of acyclic alkanes and alcohols

The C-13 NMR chemical shifts of acyclic alkanes and alcohols are reproduced by an equation having two parameters, the charge on the carbon atom as cal culated by iterative partial equalization of orbital electronegativity and the effective number of hydrogen atoms three bonds away from the carbon ato m under consideration. The data sets consist of 183 carbons of all alkane i somers up to C-8 and 184 carbons of aliphatic alcohol isomers up to C-8. Th e alkane carbons are correlated with a correlation coefficient of 0.994 and a standard deviation of 1.06 ppm and the alcohol carbons with a correlatio n coefficient of 0.997 and a standard deviation of 1.37 ppm. The influence of effective number of hydrogen atoms three bonds away is discussed in term s of 1,4 steric interactions in the molecules. Copyright (C) 1999 John Wile y & Sons, Ltd.