I. Infra-Red Studies of Nitrous Acid, the Chloramines and Nitrogen Dioxide. II. Observations Concerning the Photochemical Decomposition of Nitric Oxide

Citation

Moore, Gordon Earle (1954) I. Infra-Red Studies of Nitrous Acid, the Chloramines and Nitrogen Dioxide. II. Observations Concerning the Photochemical Decomposition of Nitric Oxide. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/K3MR-VX06. https://resolver.caltech.edu/CaltechETD:etd-01232004-112159

Abstract

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. 1. The results of an investigation of the infra-red spectra of gaseous nitrous acid and deutero-nitrous acid in the region to 25? have been combined with previous data in the 1.4-15? region to make a complete vibrational assignment. Nitrous acid exists as a pair of rotational isomers which we believed to be the cis and trans forms, The cis form is of higher energy by 500 ? 250 calories mole[^-1]. From rotational constants and by comparison of force constants with those of molecules of known structure sets of structural parameters for both species have been obtained, from which conclusions are drawn regarding the electronic structure of nitrous acid. The barrier for hindered rotation of the hydrogen atom about the nitrogen-oxygen single bond has been approximated by a three-term series, which suggests a maximum barrier height of about 12 kcal. mole[^-1]. The standard entropy of an equilibrium mixture of cis and trans nitrous acids at 25[degrees] has been calculated to be 56.0 e.u., to be compared with 54.0 e.u., and 54.8 e.u. for the pure trans and cis isomers, respectively. 2. The infra-red vibration spectra of gaseous NH2Cl, NHDCl, NHCl2 and NCl3 were investigated from 1.4 to 25?. Several fundamental vibrations were identified, and the large rotational constants were evaluated for NH2Cl, NHDCl and NHCl2. With the assistance of reasonable assumptions regarding other parameters these were used to calculate an H-N-Cl angle of 102[degrees] in NH2Cl and suggest that [?]Cl-N-1 =106[degrees] and [?]=1.76 [Angstrom] in NHCl2. These parameters are interpreted on the basis of simple electronic considerations. 3. The infra-red spectrum of NO2 has been reinvestigated in the 1.4-3.4? region under high dispersion. The nine bands observed show resolvable rotational structure and the moments of inertia obtained, in conjunction with the large rotational constant from measurements of [?] by Wilson and Brown, yield the ground state parameters r[?] = 1.188? 0.004 [Angstrom] and [?]. The set of overtones and combinations observed together with [?] from Wilson and Brown allow one to determine a complete set of quadratic vibrational interaction constants. The frequencies of NO2 are [?]. An intensity alternation is observed in type A bands as is predicted by theory but which, as far as the author is aware, has not previously been observed in a similar case. An apparently abnormal interaction which is not adequately explained occurs between the vibrational levels [?] and [?] and likewise between [?] and [?]. 4. Section II describes briefly some experiments concerning the photochemical decomposition of nitric oxide. It was shown that absorption to the 0,0 and 1,0 [?] under conditions where these bands are pressure broadened leads to photochemical decomposition. Nitrogen was shown to effect the rate of decomposition only slightly when added to nitric oxide at 15 cm of Hg pressure. This decomposition is of interest because of its possible connection with the problem of the heat of dissociation of nitrogen.

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