Please login first
The interaction of the molecule unconnected fragments in ω-arylaliphatic acid esters.
1  Ukrainian Academy of Printing, Lviv, Ukraine

Abstract: At the XIV Conference ECSOC (2010), we made the first post, which opened a new section of our research - the study of influence on each other through the space of two molecule fragments, unconnected by chemical bonds, at the time of registration of NMR spectra. In this investigation it was found that the aryl ring has the greatest influence on the spectral parameters of the studied fragment of the molecule, which is separated from the aryl groups by one or more chemical bonds. In the present communication we conduct systematic investigation of the described phenomenon researching the methyl and ethyl esters of ω-aryl fatty acids by general formula: Ar-(CR1R2)m-X-(CR3R4)n-COOAlk, where Alk = Me or Et, and X = N or O. We have studied such esters: i) of aromatic acids (m = n = 0, heteroatom X in them missing), i.e. unsubstituted and substituted benzoic (1), α-naphthoic (2); ii) of ω-arylcarbonic acid (m = 0, heteroatom X in them missing): arylacetic (3) (n = 1), β-arylpropionic (4) (n = 2) and γ-arylbutyric (5) (n = 3), as well as iii) acids, in which the alkyl moiety of the molecule acidic fragment contains heteroatom X (nitrogen or oxygen) (6). The presence or absence of the aryl fragment influence on the alkoxy group was judged on the value of the basic spectral parameters - the chemical shifts of methyl protons (δСН3Н) as well as (δСН2Н and δСН3Н) in ethyl groups. There were developed and validated specific criteria for identifying such effect. One of them is based on the introduction of a new virtual parameter - the expected value of the chemical shift of alkoxy group protons. By the sum of the results, obtained using all the necessary criteria, we make judgments about the probability of the presence or absence of the studied effect. There were suggested the presence of studied effects in ethers 3-6, and its absence in the esters 1 and 2, with the exception of esters of substituted benzoic acids (1), in which the substituent in the ortho-position is aryl group. Based on the virtual differential ∆δСН2Н and ∆δСН3Н ​​ parameters values (which is equal to the difference between "experimentally obtained" and "expected" values ​​of the basic spectral parameters δСН2Н or δСН2Н), as well as other criteria, we make judgments about the magnitude of the studied effect in esters 3-6 as well as its dependence on the values ​​of m, n, and X. A comparison of aryl group "influence magnitude" aryl group on the protons of methyl and methylene fragments of ethoxyl group. We make the overall conclusion about high probability of the studied effect existence in esters 3-6 and, especially, in compounds 3 and 4.