Glyoxal, CHO

Glyoxal, (CHO)s.—There have been a number of calculations on the ground state of this molecule, and very recently a more detailed study of several excited states. 

Ha also used a standard geometry for both cis and trans forms and with a near DZ basis he obtained a value of only 13 kJ for the cis-trans separation. This result is probably because the choice of geometry was far from the optimum. Pople and coworkers obtained a lower energy with a 4-31G basis set which should be less than DZ quality. 

Sundberg and Cheung used a somewhat smaller than DZ basis set and per- 

A more extensive set of geometry optimization calculations was reported by Dykstra and Schaefer. A contracted DZ basis gave a lower SCF energy than in previous work and the results for the cis-trans separation are compared with the earlier work in Table 9. All five structural parameters were optimized and shown to give improvements in the results. The nature of the molecular orbitals was analysed in detail. Table 9 summarizes the results for the ground state. 

Reference trans Energy cis-trans Separation Barrier  

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Similarly, there is some experimental evidence for surface reactions of organics. For example, Schweitzer et al. (1998) report evidence for a surface reaction (probably protonation) of glyoxal, (CHO)2, on acid surfaces at temperatures below 273 K. 

The destruction of acetylene in the atmosphere occurs only by reaction with OH radicals (Siese and Zetzsch 1995). Typical products are HO2, glyoxal (CHO—CHO), but SOA formation (Volkamer et al. 2009) is also found under laboratory conditions. The polymerization of C2H2 after radiolysis has long been known. 

Gruber-Stadler, M., M. Muhlhauser, and C.J. Nielsen (2006), Ah initio MRD-CI investigation of the electronic spectrum of glyoxal (CHO)2, Molec. Phys., 104, 2515-2521. 

Examples include acetaldehyde, CH CHO paraldehyde, (CH CHO) glyoxal, OCH—CHO and furfural. The reaction is usually kept on the acid side to minimize aldol formation. Furfural resins, however, are prepared with alkaline catalysts because furfural self-condenses under acid conditions to form a gel. 

Eleostearic acid, Ci8H30O2( is a rare fatty acid found in the tung oil used for finishing furniture. On ozonolysis followed by treatment with zinc, eleostearic acid furnishes one part pentanal, two parts glyoxal (OHC—CHO), and one part 9-oxononanoic acid [0HC(CH2)7C02H]. What is the structure of eleostearic acid ... 

Ozonolysis was once used to locate the position of a double bond (or bonds) in unsaturated compounds of unknown structure—largely because of the ease of characterisation of the carbonyl products— but has now been superseded by physical methods, e.g. n.m.r. spectroscopy, which are easier and quicker. Benzene forms a triozonide which decomposes to yield three molecules of glyoxal, OHC—CHO the sole reaction of benzene that suggests it may contain three real double bonds in a Kekule structure Alkynes also undergo ozonolysis, but at a much slower rate than alkenes. 

Abb. 12 zeigt drei Banden ausdem von A. R. H. Cole undH.W. Thompson (49 c) untersuchten Schwingungsspektrum des Glyoxals (OHC-CHO),... 

The observation of the a-dicarbonyls glyoxal (CH(O)CHO), methyl-glyoxal (CH3C(0)CH0), and biacetyl (CH3C(0)C(0)CH3) in significant... 

CHO)2 (c). Estimating the Washburn2 correction to be —0.15 per cent, we have computed from the data of deForcrand3 (see Kharasch1) the heat of combustion of glyoxal to be 172.0. 

Another important use of SeOj is in the oxidation of CH3 groups to CHO, but not to COOH group. But such CH3 group must be activated by a carbonyl or other group. Thus phenyl glyoxal has been prepared in about 72% yield by refluxing a solution of acetophenone in the medium of dioxane for about 4 hours. 

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