Formyl Hydrogen Research Articles

Studies of enzyme-mediated reactions. Part 11. Experiments on the dismutation of aldehyde to alcohol and carboxylic acid by the complex of liver alcohol dehydrogenase and NAD+

[1-3H1] Heptanal undergoes dismutation in the presence of the complex of liver alcohol dehydrogenase and NAD+ to yield unlabelled heptanoic acid and (1RS)-[1-3H1]heptanol with double the specific radioactivity, thus demonstrating transfer of the formyl hydrogen from one half of the sample to the other. Conditions are found for reducing the incidence of this dismutation process.

The microscopic reaction dynamics and branching ratio in the F + HCOOH and F + H 2CO reactions

Infrared chemiluminescence under conditions of arrested relaxation has been applied to the study of the hydrogen and deuterium abstraction reactions of HCOOH, DCOOH and H 2CO with F atoms. Two distinctly different modes of product excitation are observed, depending upon whether the reaction proceeds via the formyl or carboxyl hydrogen. Reaction at the formyl hydrogen (or deuterium) causes substantial inversion in the diatomic product internal energy distributions. The F + H 2CO and F + DCOOH reactions respectively channel 56% and 54% of the available energy into vibration in the product diatomic when they occur at the formyl site. In both cases the product energy distributions are qualitatively similar to those observed in direct reactions of triatomic systems on repulsive energy surfaces. In contrast to these, reaction at the carboxyl hydrogen of DCOOH gives an HF† product vibrational distribution having a Boltzmann equilibrium shape at a temperature of 4300 K. The ratio of HF to DF product from the F + DCOOH study shows that reaction occurs at the carboxyl hydrogen approximately twice as often as at the formyl site. Comparison with triatomic reactions involving the same mass-combinations implies that abstraction of the formyl hydrogen occurs via single-collision, direct encounters, whereas reaction at the carboxyl site involves a long-lived complex in which extensive randomisation of the reaction exoergicity among all the product vibrational modes can occur.

ChemInform Abstract: REACTIONS OF METHYL RADICALS WITH ACETALDEHYDE AND ACETALDEHYDE‐D1. I. RELATIVE RATES OF ATOM ABSTRACTION REACTIONS AT 785°K

The role of ethenoxy radicals in the pyrolysis of CH3CDO was studied by mass spectrometric analysis of the isotopic composition of the methane, ethane, and recovered aldehyde. Experimental evidence was obtained for the formation of ethenoxy radicals and for their reaction with acetaldehyde. Mixtures of CH3CHO and CH3CDO were pyrolyzed in order to minimize H-D scrambling in the methyl group of the aldehyde. A kinetic treatment of the methyl radical reactions and furnished the rate constant ratios (k2a + k2b)/k1a = 2.7 and k1b/k1a = 0.62 at 785°K. It is concluded that at the usual temperatures of CH3CHO pyrolysis the rate of alkyl hydrogen capture is comparable to that of formyl hydrogen abstraction. The results and conclusions are discussed and compared with previous work.

Reactions of methyl radicals with acetaldehyde and acetaldehyde‐d1. I. relative rates of atom abstraction reactions at 785°K

AbstractThe role of ethenoxy radicals in the pyrolysis of CH3CDO was studied by mass spectrometric analysis of the isotopic composition of the methane, ethane, and recovered aldehyde. Experimental evidence was obtained for the formation of ethenoxy radicals and for their reaction with acetaldehyde.Mixtures of CH3CHO and CH3CDO were pyrolyzed in order to minimize H‐D scrambling in the methyl group of the aldehyde. A kinetic treatment of the methyl radical reactions equation image and equation image furnished the rate constant ratios (k2a + k2b)/k1a = 2.7 and k1b/k1a = 0.62 at 785°K. It is concluded that at the usual temperatures of CH3CHO pyrolysis the rate of alkyl hydrogen capture is comparable to that of formyl hydrogen abstraction.The results and conclusions are discussed and compared with previous work.

Formation of free radicals in photoirradiated cellulose. V. Effect of temperature

AbstractESR spectra of purified and ferric ion‐sensitized celluloses irradiated with ultraviolet light in vacuo at 45, 20, −80, and −196°C were recoreded and compared. Generally, several kinds of spectra, viz., singlet, three‐line, five‐line, and seven‐line spectra, were observed. At higher temperatures, only singlet and three‐line spectra of stable free‐radical species were detected, whereas at lower temperatures such as at −196°C, two doubled spectra of formyl radicals and hydrogen atoms were also detected in addition to cellulose radicals. It is believed that the intricate spectra observed at low temperatures are superimposed upon spectra generated by free radicals which may or may not be stable at high temperatures. During reirradiation at −196°C with an alternative light sources, i.e., λ > 2537 Å and λ > 3400 Å, of samples which were irradiated at 20°C or at −196°C, phenomena indicative of radical transformation and formation of new radicals or of decay of radicals in terms of ultraviolet bleaching were observed on studying the changes of line‐shapes and relative signal intensities of the spectra.

Formation of aniline‐like ions by electron‐impact‐induced elimination of CO from formanilide

AbstractThe metastable peak intensity ratios for elimination of HNC vs DNC from the [M  CO]+· ion of deuterium labelled analogues of formanilide show that the formyl hydrogen atom migrates to nitrogen prior to or during CO expulsion to form a [C6H7N]+· ion of aniline‐like structure. An examination of metastable peaks does not allow similar conclusions to be reached for methyl substituted formanilides. Low abundance [C6H6O]+· ions are formed by HNC elimination from the formanilide molecular ion in a reaction where three covalent bonds to the formyl carbon are broken.

ChemInform Abstract: AN UNUSUAL OXIDATION OF THE FORMYL HYDROGEN ATOM OF FORMAMIDES BY SELENIUM

Elemental selenium was found to oxidise the formyl hydrogen atom of dimethylformamide in the presence of alkoxide to give alkyl NN-dimethylcarbamate under mild conditions.

The [formula omitted] transition of formic acid

New sharp bands of formic acid have been observed in the near ultraviolet at the long wave-length end of the previously observed diffuse band system (2250–2500 Å) by considerably extending the absorption path length. Both the diffuse and sharp bands belong to the same vibrational system which is assigned to the π ∗ ← n electronic transition in the carbonyl group. Extensive progressions are observed in the carbonyl stretching frequency which is greatly reduced in the excited state (fundamental ν 3′ ≈ 1080 cm −1) and many intervals of about 400 cm −1 are assigned to the OCO bending frequency ν 7′. A band contour analysis of the 2593 Å band shows that the molecule is nonplanar in the excited state because of the magnitude and sign of the inertial defect. From this analysis, the rotational constants for the excited state are S ‘=1.8755, B ‘0.4042, C ‘=0.3378 cm −1 By the plausible assumption that the important changes in the molecule are in the C=0 bond length, the OCO angle, and the nonplanarity due to the formyl hydrogen, the following excited state parameters are derived. rC=0 = 1.407 A.The changes in formic acid are closely analogous to the changes in formyl fluoride as a result of the π ∗ ← n transition.

An unusual oxidation of the formyl hydrogen atom of formamides by selenium

Elemental selenium was found to oxidise the formyl hydrogen atom of dimethylformamide in the presence of alkoxide to give alkyl NN-dimethylcarbamate under mild conditions.

Formic acid reduction. XXI. Reductive cleavage reaction of p-dimethylamino-substituted triphenylmethanes induced by formate.

On heating with the formate, triethylammonium formate, known as the distillable liquid given by 5HCO2H·2NEt3, several triphenylmethanes possessing dimethylamino group on their benzene rings have been shown to suffer reductive cleavage at the carbon bond bound to the dimethylaminophenyl carbon to give N, N-dimethylaniline and diphenylmethanes. The reaction is controlled by the structure and the substituent effect. Isotopic experiments using a deuterated formate has revealed that formyl hydrogen of formic acid is transferred to the methylene carbon of the diphenylmethane product. From the assembled data, a possible mechanism is proposed.

Photolysis of Formaldehyde as a Hydrogen Atom Source in the Lower Atmosphere

The rates of formaldehyde photodecomposition into hydrogen and formyl radicals and hydrogen and carbon monoxide molecules in sunlightirradiated atmospheres have been estimated from extinction data and photochemical results. These data should prove useful in the development of models for the chemical changes that take place in the polluted atmosphere.

Kinetics of hydrogen abstraction by difluoroamino radicals from n-propyl formate and the n-propoxycarbonyl radical decomposition

The kinetics of the formyl hydrogen abstraction by difluoroamino radicals from n-propyl formate, using tetrafluorohydrazine as a thermal source of these radicals, has been studied between 398 and 463 K. The rate equation for this abstraction was given by log[k/(ml mol–1 s–1)]=(8.48 ± 0.88)–(77800 ± 7200)/2.3RT where R= 8.314 J mol–1 K–1. The decomposition reaction of the resulting n-propoxycarbonyl radical was also studied. No pressure dependence on this decomposition of the radical was observed in this temperature range and in the pressure range 11–76 Torr. The rate equation was given by log(k/s–1)=(14.11 ± 0.89)–(53000 ± 7300)/2.3RT where R= 8.314 J mol–1 K–1.

Formic Acid Reduction. XIII. Formate Reaction of the Compounds possessing the Carbon Bound to Both Oxygen and Nitrogen

There has been introduced a new type of formic acid reduction of the compounds in which both amine nitrogen and ether oxygen are bound to the same carbon. With series of N-(α-butoxybenzyl) dialkylamines, N-(butoxymethyl) dialkylamines and 3-methyloxazolidines, the reaction was normally carried out on heating with distillable formate, TMAF given by 5HCO2H·2N (CH3)3, to give tertiary amines, resulting in reductive fission at the carbon-oxygen bond. Mode of the reduction was clarified by the technique of using deuterated formic acids, in which formyl hydrogen of formic acid is transferred to the carbon of the carbon-oxygen bond. On the basis of this result a possible mechanism is described.

Photoamidation of olefins—I : The electronic structure and properties of ground and excited states of formamide

The modified CNDO-CI method is applied for an analysis of electronic properties of formamide in its ground and excited states. Results obtained from the total wave function are in complete agreement with available data. The unobserved first triplet of formamide is predicted to be of n 0 → π* type, located at 4-2 eV; this result indicates that in the photoamidation of olefins, the only role of excited acetone is the abstraction of the formyl hydrogen of ground formamide.

ESR Studies on the Reaction of an OH Radical in α,β-Unsaturated Aldehyde

Abstract ESR studies on the UV irradiated α,β-unsaturated aldehyde - hydrogen peroxide mixtures have been done at low temperature in order to examine the reactions of an OH radical with aldehyde: formyl hydrogen-abstraction, methyl hydrogen-abstraction, and addition to an olefinic bond. It has been shown that abstraction of a methyl hydrogen by an OH radical occurs in croton-aldehyde, whereas β-addition of an OH radical to an olefinic bond takes place in methacrolein and acrolein. A formyl hydrogen is unreactive with an OH radical in any case. The distribution of unpaired electron in the radicals was also discussed.

Ion–molecule reactions in formic-d acid and methyl formate

The following ion–molecules reactions have been found to occur in DCOOH for ions produced by bombardment with electrons of 10–15 eV energy (all rate constants in cm3 molecule−1 units).[Formula: see text]In methyl formate the following reactions have been identified and rate constants measured for ions formed by bombardment with electrons of 10–15 eV energy.[Formula: see text]Experiments using DCO2CH3 show that reaction [f] involves transfer of the methyl hydrogen at a rate 1.5 times that of the formyl hydrogen while reaction [g] involves transfer from only the methyl position of CH3OH+. The rate constants for all reactions are considerably higher than predicted on the basis of ion–induced dipole interactions only but are in good agreement with values calculated by including ion–dipole interactions.