The Influence of Methyl Group Position on the Chemical Shifts Values of all Protons in the 1H NMR Spectra of Trimethylalkane Molecules

Abstract

The protons chemical shifts values in the PMR spectra of trimethylalkanes of general formula N 1 ,N 2 ,N 3 -n (when n is the letter designation of linear alkane, and N 1 , N 2 ,N 3 are the carbon atom numbers which are attached to the methyl groups in the alkyl chain of n) of 4 trimethylalkane families (2,2,5-n; 2,2,4n; 2,2,3-n and 2,3,4-n) have analyzed. It is calculated and discussed the individual (N 1 ,N 2 ,N 3 -n-i), the arithmetic means (N 1 ,N 2 ,N 3 -n-i) "standard" differential parameters (the difference between absorption of studied proton in N 1 ,N 2 ,N 3 -n and its absorption in the n) and the "integral spectral changes" Σ N 1 ,N 2 ,N 3 -n-i that occur in process n → N 1 ,N 2 ,N 3 -n). Also it is calculated and discussed the individual first (N 1 ,N 2 ,N 3 -n'i), second (N 1 ,N 2 ,N 3 -n''-i) and the arithmetic means (N 1 ,N 2 ,N 3 -n'-i) additional differential parameters (the difference between absorption of studied proton in N 1 ,N 2 ,N 3 -n and its absorption in the correspondent monomethylalkane Nn or dimethylalkanes N 1 ,N 2 -n).

The Influence of the Methyl Group Position on the Chemical Shifts Values of all Carbon Atoms Nuclei in 13C NMR Spectra of Monomethylalkane Molecules

“…As previously [1][2][3], the difference between the chemical shift of the every i-th type of carbon atom nuclei (C i ) in discussed now monomethylalkane Nn and the same i-th type of carbon atom nuclei in the "standard (etalon) compound", which we denote as (etal), we designate as the differential spectral parameter «Δδ C,Nn i » (abbreviated DSP). The corresponding linear alkanes n with the same number of carbon atoms taken as "standard (etalon) compound" for each family of the linear alkanes Nn.…”

“…In our previous communications we considered and discussed the peculiar properties of individual "standard" differential parameters (the difference between absorption of studied hydrogen nuclei in mono- [1], di- [2] and trimethylalkanes [3] and absorption of similar nuclei in the unsubstituted linear alkane). In the present study, we consider the change in the 13 C NMR spectral properties of the corresponding carbon atom's nuclei during the transition from an unsubstituted linear alkane to monomethylalkane molecule.…”