0000000000515295
AUTHOR
Maija Pitkänen
13C NMR study of some polychloro-isobutane and -isobutene compounds
The 13C chemical shifts and the carbon–proton coupling constants have been determined for some chlorinated isobutane and isobutene compounds. The one-bond coupling constants in isobutane derivatives showed a regular increase with an increasing number of γ-chlorine substituents. The three-bond coupling constant of the methyl carbon decreased from 4.2 to 2.0 Hz as the number of chlorine substituents in the γ-position increased. In the isobutene compounds, the vicinal coupling of C-1 was larger to protons in a group that is trans with respect to a chlorine substituent on C-1 than to those in the corresponding group cis to the chlorine. The vicinal coupling constants between atoms in geminal gr…
Multinuclear NMR study of 1,3,3-trimethylbicyclo[2.2.1]heptan-2-one (fenchone) and its six monochlorinated derivatives
1H, 13C and 17O NMR spectra of fenchone and six monochlorofenchones have been recorded. The second-order 1H NMR spectra were analysed by an iterative computer program. The 1H and 13C chlorine-induced substituent chemical shifts (SCS) were calculated. The vicinal coupling constants proved to be essential in the assignment of the chemical shifts of the geminal methyls. No clear correlation was observed between the chemical shifts of the carbonyl oxygen and the carbonyl carbon. All monochlorofenchones were previously unknown compounds and were synthesized for this work.
13C spin-lattice relaxation study of chlorinated alkanes
The spin-lattice relaxation of ten polychloroalkanes (ethanes to pentanes) have been studied both neat and in a 50% solution in CDCl3. The T1 values for the CH2, CH2Cl and CHCl2 carbons decrease with increasing molecular weight in accordance with a dipolar-dominated mechanism, whereas those of the CCl3 carbons showed no dependence on molecular weight. In chloropentanes, with chlorine substitution at one end only, the frequency of segmental motion begins to compete with that of overall tumbling of the molecule. Consequently, the T1 minimum is shifted from the middle towards the heavier end of the molecule, and also a relatively large T1 for the terminal methyl is observed. It was also demons…
13C NMR study of aromatic ring-substituted (E)-3-phenylpropenals and (2E,4E)-5-phenylpenta-2,4-dienals
13C and 1H chemical shifts together with C,H and H,H coupling constants are presented for (E)-3-phenylpropenal, (2E,4E)-5-phenylpenta-2,4-dienal and their o-OCH3- and o-, m- and p-NO2-substituted derivatives. The SCSs calculated for the aldehyde chains show similar effects on the ring carbons, except in the para position where the shorter chain causes a 3.3 ppm deshielding and the longer chain a 1.0 ppm shielding effect. This shift difference is reflected in all the ring-substituted derivatives of the two series of aldehydes, but not in the one-bond C,H coupling constants. The effect of aromatic ring substitution on 2J(C,CHO) seems to be mainly inductive in origin. The importance of the str…
Conformational study of methyl esters of some aliphaticerythro- andthreo-dichlorocarboxylic acids
The average conformations of methyl esters of some aliphatic erythro- and threo-dichlorocarboxylic acids in dilute carbon tetrachloride solutions have been determined from the vicinal proton–proton coupling constants and 1H NMR shifts. The 13C shift differences between the erythro and threo forms are compared and discussed with regard to the differences in the average conformations.
1H NMR and IR spectra of methyl dichloropropanoates and butanoates
Abstract Methyl dichloropropanoates and butanoates were synthesized and their 1H NMR and IR spectra were studied. Comparisons were made with the spectral characteristics of corresponding monochlorocompounds. Special attention was given to the elucidation of the characteristic spectral features associated with particular chlorine substitution patterns. The 1H NMR of erythro and threo methyl 2,3-dichlorobutanoates were analyzed using a computer program MAOCON, a modified LAOCOON 3 program. In the spectrum of the threo form the order of the chemical shifts of protons on asymmetric carbons seems to be opposite to that reported in earlier literature. Also vicinal coupling constants J23 were foun…
A new synthesis and crystal structure of n-(2-hydroxyethyl)succinimide
Abstract N-(2-Hydroxyethyl) succinimide was formed with 80 % yield in the reaction of 2-oxazolidinone with succinic anhydride at 210° C instead of polyesteramides obtained from N-substituted 2-oxazolidinones. The identification based on the crystal structure determination.
The combined effects of two chlorine substituents and the non-additivities of chemical shifts in aliphatic dichloro esters
Carbon-13 NMR spectra were measured for 25 methyl esters of aliphatic dichlorocarboxylic acids for substituted propanoic to hexanoic acids. Observed 13C shifts are compared with calculated shift values obtained from the shifts of the corresponding monochloro esters by applying a simple sum method. The greatest failures from additivity are observed for αβ and αα substituted carbons. The combined effects of two chlorine substituents were determined, and compared with those obtained from chlorine substituent effects in monochloro esters by assuming additivity. The trends displayed by the combined effects, and also by the non-additivity effects, are discussed.
13C NMR, 1H NMR and IR spectra of a series of monochloroesters of aliphatic short chain carboxylic acids
Abstract 13 C chemical shifts for 14 isomeric monochloroesters of aliphatic carboxylic acids from propanoic acid to hexanoic acid have been determined. Comparisons are made with the literature values for methyl monochloro-octanoate isomers. Substituent effects for all positions are given. Characteristic IR absorption bands are presented and comparisons are made with regard to the isomeric structure. Connections are suggested between observed trends in IR absorption frequencies and some “abnormal” chlorine substituent effects on 13 C chemical shifts. 1 H NMR spectra of these compounds are considered.