Examination of the Matrix Isolation Fourier Transform Infrared Spectra of Organic Compounds: Part II

Abstract

Matrix-isolated (MI) Fourier transform infrared spectra have been collected on a series of aliphatic ketones. The values for the carbonyl absorptions maxima are intermediate between vapor-phase (VP) and solid-state solution (SS) phases. The data reveal a stereochemical influence on the position of the ketone carbonyl absorption when the carbons that are in the alpha position with respect to the carbonyl group contain alkyl snbstituents vs. protons. Steric bulk causes the frequency of the absorption to decrease. The position of the ketone carbonyl absorption was also shown to decrease as the carbonyl group migrated toward the center of a long straight-chain hydrocarbon backbone. Stereochemical influences due to ring strain were also documented. Unsaturation, located in the alpha position with respect to the carbonyl, was shown to reduce the absorption frequency. The trends found in this MI study are comparable to those previously documented from VP and SS studies. In two cases wherein very bulky substituents were located in the alpha position with respect to the carbonyl, a splitting of the carbonyl absorption was observed. Studies are underway to test for a general trend in and to uncover an explanation for this phenomenon.

Infrared and reflectron time-of-flight mass spectroscopic analysis of methane (CH4)–carbon monoxide (CO) ices exposed to ionization radiation – toward the formation of carbonyl-bearing molecules in extraterrestrial ices

“…However, ketones with higher alkyl groups such as ethyl and propyl can also contribute to this band. 65 The feature at 1701 cm À1 can be assigned to a,b-unsaturated aldehydes/ketones as a 20-30 cm À1 redshift can be attributed to the a,b unsaturation and hence lowering of the frequency due to resonance. 66 Finally, the broad infrared absorption band at 1660 cm À1 can be linked to a,b-dicarbonyl compounds in keto-enol form, a,b,g,d-unsaturated aldehydes/ketones, and a combination of both, i.e.…”

The Lewis Acidity of the BO Triple Bond in Methyl(oxo)­borane

“…The 1· N(CH 3 ) 3 complex is isoelectronic with the ketone 3, 3‐dimethylbutane‐2‐one, while 1· py is isoelectronic to acetophenone. These ketones have their CO stretching vibrations at 1718 cm –1 and 1699 cm –1 , respectively, under matrix isolation conditions 47. Hence, the complexes of 1 with these nucleophiles resemble their isoelectronic ketones to a large degree.…”

Investigation of the mechanism of ozonolysis of (Z)-3-methyl-2-pentene using matrix isolation infrared spectroscopy

“…Multiple species are possible from the O atom addition to MP, including acetaldehyde, 2-butanone, 3-methyl-2-pentanone, 2-methyl-3-pentanone, and 2-2-dimethylbutanal. Based on the lit- erature spectra where available [32,34,35], and computed spectra where literature spectra are not available, all of these possible products have C@O stretches within a few wavenumbers of one another, with nearly identical 18 O shifts. Thus, specific identification of a single product is very difficult and, given the breadth of the product absorption, it is likely that more than one product is formed and absorbs within the band envelope that is observed.…”