Hydrogen chloride, absorption band

Two pieces of direct evidence support the manifestly plausible view that these polymerizations are propagated through the action of car-bonium ion centers. Eley and Richards have shown that triphenyl-methyl chloride is a catalyst for the polymerization of vinyl ethers in m-cresol, in which the catalyst ionizes to yield the triphenylcarbonium ion (C6H5)3C+. Secondly, A. G. Evans and Hamann showed that l,l -diphenylethylene develops an absorption band at 4340 A in the presence of boron trifluoride (and adventitious moisture) or of stannic chloride and hydrogen chloride. This band is characteristic of both the triphenylcarbonium ion and the diphenylmethylcarbonium ion. While similar observations on polymerizable monomers are precluded by intervention of polymerization before a sufficient concentration may be reached, similar ions should certainly be expected to form under the same conditions in styrene, and in certain other monomers also. In analogy with free radical polymerizations, the essential chain-propagating step may therefore be assumed to consist in the addition of monomer to a carbonium ion... 

Gilbert N, Sheppard AS (1973) Infra-red spectra of the hydrates of hydrogen chloride and hydrogen bromide. Absorption bands of the H502+ species. J Chem Soc Faraday Trans II 69 1628-1642... 

Orlova N. D., Pozdniakova L. A. Profiles of infrared absorption bands and rotational motion of molecules in liquids. Quantum rotation of hydrogen-chloride molecules, Opt. Spectr. 35, 624-7 (1973). [Optika i Spectr. 35, 1074-7 (1973)]. 

Spectrum.—According to J. Tyndall,18 hydrogen chloride and hydrogen bromide absorb heat rays. W. H. Julius found that hydrogen chloride had an absorption band for the wave-length 3 68[i and K. Angstrom and W. Palmaer at 3 41/u,. W. de W. Abney and E. R. Festing found liquid hydrochloric acid had very feeble absorption lines in the ultra-red at 732, 741, 845, 867, and 949/u/i. 

In water, at ordinary concentrations, the hydrogen chloride is practically all present as the hydrated ions. The infrared absorption bands characteristic of HCl, and shown by the liquid hydride and its solutions in nonionizing solvents do not appear in the aqueous solutions.451 In dilute solutions, the conductivities agree with the Debye-Huckel-Onsager formula. 

The number of suitable solvents is limited and the most widely used are carbon tetraddoride and carbon disulphide because they have relatively few absorption bands in the infra-red region. Other solvents which may be used include chloroform, ethylene dichloride, methylene chloride, boizene, cyclohexane, and heptane. The concentration of the compound is usually about 5 to 10%, but concentrations up to 20% w/v can be employed. With these high concentrations, hydroxyl and amino compounds often exhibit bands due to intermolecular hydrogen bonding. 

Elsewhere, in the mid-IR, photon energy is sufficient to modify the quantized terms vib and iJjo in expression 10.2. This is therefore a vibration-rotation spectrum, that is, several tens of rotational transitions accompany each vibrational transition. For the simplest molecules it is possible to interpret particular aspects of the absorption bands. Experience and theory have enabled rules of the permitted transitions to be drawn up. Small molecules as carbon monoxide and hydrogen chloride (Figure 10.5) have been intensely studied from this point of view. 

The absorption cross sections (Figure 4.50) for hydrochloric acid (or hydrogen chloride) HC1 were measured by Vodar (1948), Romand and Vodar (1948), and Romand (1949), and later by Inn (1975). The latter measurements extend from 140 to 220 nm, leading to a photodissociation frequency of about 3 x 10-6s-1 at zero optical depth. To calculate Jhci in the atmosphere, the Schumann Runge bands and continuum must be considered, as well as the Herzberg continuum. 

Both technological and atmospheric radiation are mostly associated with water vapor and carbon dioxide, which are significant emitters and absorbers. Other examples of gases of significant emission and absorption properties are carbon monoxide, sulfur dioxide, ammonia, and hydrogen chloride. In general, radiation occurs over a number of discrete bands of the electromagnetic spectrum (recall Fig. 8.2). However,... 

The structure —CHC1—CH2—CO—CH2 — was found by Kwei [99] in polyvinylchloride after photo-oxidation. Such j3 chloroketones decompose by the Norrish type I mechanism without loss of chlorine atoms. Hydrogen chloride is obtained only when polyvinylchloride is photo-oxidized above 30°C [98]. It seems that zipper dehydrochlorination plays little role in the reaction occurring on exposure to ultraviolet light at temperatures below 150°C in the presence of air [97], and that hydrogen chloride is mainly a product of thermal decomposition rather than photolysis [98], The following mechanism can be proposed which takes into account the experimental results namely, that chain scission and crosslinking occur simultaneously on irradiation at 253.7 nm [100] and that carbon dioxide is evolved, while an absorption band at 1775 cm-1 (ascribed to peracids) is detected in the infrared spectrum [98]. 

---