The 'H, 13C and 77Se chemical shifts and the 'aC(Me)H(Me)l, "*J(SeC) and *J(SeH) coupling constanis in 14 paraor meta-substituted selenoauisoles, R-C6H.,+CH3, have been measured and the dependence of these parameters on the electronic effects of the substituent R is discussed. A signiscant (up to 6ppm) deviation from additivity of the substituent influence on the shielding of the 13C ring carbons has been found.

The 170 chemical shifts have been measured for 51 a,&unsaturated and aromatic ethers. A good linear relationship is found between the "0 chemical shifts in a series of dialkyl and the corresponding alkyl vinyl ethers. Hence, the extent of p,m-interactions between the oxygen atom and the vinyl group in the latter series does not, apparently, depend upon branching at the a-carbon atom in the alkyl moiety of these ethers. The PhOBu' ether, however, as compared to the other alkyl phenyl ethers, shows signi6cantly weakened p,m-interaction, which is apparently related to the steric hindrance of this interaction. The effects of two unsaturated groups upon the "0 chemical shifts in the corresponding ethers are non-additive. This is undoubtedly a result of 'rivalry' between these groups for conjugation with the lone electron pairs on the ethereal oxygen. The "0 chemical shift ranges of substituted methyl and vinyl phenyl ethers are nearly equal (=30 ppm). An analysis of the "0 shielding for cyclopropyl ethers shows no observable p,a-conjugation in these compounds. Excellent correlations (r>O.99) between the values of 1 7 0 chemical shifts and the calculated (MO LCAO SCF, CNDO/Z) =-electron charges on the corresponding oxygen atoms look promising for experimental estimations of m-electron densities on the ethereal oxygen.

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