Quantitative Infrared Analyses of Mixtures of Isomeric of Closely Related Substances

Abstract

proton acceptors. The following results were obtained (with a sodium chloride prism). In carbon tetrachlorideIn carbon disulfide In nitrobenzene In o-dichlorobenzene (Undiluted0) 2730 cm."1 2730 cm.-1 2735 cm.-1 2740 cm.-1 2737 cm.-1• Measured with lithium fluoride prism.Cinnamaldehyde did not show a big change in its C-H frequency on changing its solvent from carbon tetrachloride (2730 cm.-1) to carbon disulfide (2715 cm.-1).2-Naphthaldehyde showed its C-H band in anisóle or carbon tetrachloride at 2720 cm.-1 and in benzene at 2710 cm.-1. It seems therefore that the intermolecular hydrogen bonding in aldehydes, which no doubt exists (1, 8), is not effective in changing their C-H frequencies materially ( 8), possibly because it is not strong enough to bring the bonded groups so near one to the other (against the van der Waals repulsion) as to effect an appreciable change of the C-H frequency.