The Basic Strength of Formaldehyde

McTigue, PT; Sime, JM

doi:10.1071/ch9630592

Cited by 6 publications

(6 citation statements)

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“…The formation of a chemisorbed surface complex is not unreasonable, since our previous studies of aldehyde uptake by aqueous surfaces clearly demonstrated the existence of such a state for acetaldehyde; 24 however, as discussed in ref 24 the acetalaldehyde surface complex is observable at much higher pH levels because that species has the ability to isomerize to the enolate form in interactions with OH -. The action of CH 2 O as a base, forming CH 3 O + , is also not surprising, 27,34 but the value of K 3 indicated by our data is surprising since it requires CH 2 O to act as a much stronger base in concentrated acid solutions than is indicated by the previously measured value of its basic pK a . 34 Our work does confirm earlier conclusions by Tolbert et al 27 that CH 2 O uptake on sulfuric acid aerosols will be efficient, suggesting that liquid-phase CH 2 O reactions may play an important role in upper tropospheric and stratospheric chemistry.…”

Section: Discussionsupporting

confidence: 56%

Section: Resultsmentioning

confidence: 79%

“…These results imply that at least one additional mechanism is responsible for uptake in this acidity range. We propose two additional uptake mechanisms: first, following the work of McTigue and Sime 34 and Tolbert et al, 27 the equilibrium formation of a protonated form of formaldehyde, CH 3 O + accounts for the observed uptake at high acidities and, second, in the mildly acidic range (<20 wt % acid) the observed uptake is due to the formation of a surface complex These two proposals are motivated by the following evidence. At very high acidity the formation of a CH 3 O + or similar species is necessary to explain the high observed uptake since the decreasing H 2 O activity reduces gem diol formation.…”

Section: Resultsmentioning

confidence: 90%

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Uptake of Gas-Phase Formaldehyde by Aqueous Acid Surfaces

Jayne¹,

Worsnop²,

Kolb³

et al. 1996

J. Phys. Chem.

109

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The uptake of gas-phase formaldehyde, CH 2 O, by aqueous sulfuric and nitric acid droplets has been measured as a function of temperature, acid concentration, and gas-droplet contact time. The results are interpreted in terms of the mass accommodation coefficient for formaldehyde on aqueous surfaces, the Henry's law constant for formaldehyde in aqueous acid solutions, and the liquid-phase formation kinetics of methylenediol, CH 2 (OH) 2 , and protonated formaldehyde, CH 3 O + . Time-dependent uptake studies under mildly acid solutions where CH 2 (OH) 2 and CH 3 O + formation is slow reveal the existence of a chemisorbed surface complex for CH 2 O at the gas-liquid interface. Uptake studies on nitric acid and mixed sulfuric acid/nitric acid solutions show slightly enhanced uptake relative to sulfuric acid only solutions. This observation has been attributed to variation of formaldehyde solubility (expressed as Setchenow coefficients) and CH 3 O + equilibrium constant in nitric and sulfuric acid solutions. The implications of these measurements for the aqueous acid chemistry of formaldehyde and its role in atmospheric chemistry are discussed.

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Section: Discussionsupporting

confidence: 56%

Section: Resultsmentioning

confidence: 79%

Section: Resultsmentioning

confidence: 90%

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Uptake of Gas-Phase Formaldehyde by Aqueous Acid Surfaces

Jayne¹,

Worsnop²,

Kolb³

et al. 1996

J. Phys. Chem.

109

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“…This analysis was used as a starting point for the pKBH+ assignment of Cox et al (17). For acetaldehyde and formaldehyde, the two compounds which could give a clear answer to the question, there are no accepted values for pKBH+, although several attempts have been made to measure them (19)(20)(21) If we plot the observed rate constants for acid catalyzed reaction vs. the equilibrium constants calculated for process [14] we find a rather implausible looking graph, Fig. 7, with severe scatter of the data about the best line.…”

Section: I Imentioning

confidence: 99%

Effect of the acyl substituent on the equilibrium constant for hydration of esters

Guthrie¹,

Cullimore²

1980

Can. J. Chem.

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Can. J. Chem. 58, 1281 (1980). Heats of hydrolysis have been measured for the trimethyl orthoesters of isobutyric, propionic, benzoic, methoxyacetic, chloroacetic, and cyanoacetic acids using aqueous acid with an organic cosolvent where necessary, and of the corresponding esters in alkaline solution. Solubilities or free energies of transfer from gas to aqueous solution have been measured. permitting calculation of the free energies of formation of the aqueous orthoesters, and by methods which we have published previously, calculation of the free energies of formation of the covalent hydrates of the esters, and the free energy changes for hydration of these esters.Using estimated pKa values equilibrium constants were calculated for the addition of hydroxide to the esters. The data are ingood agreement with the appropriate Marcus equation relating rate and equilibrium constants with a value forb of 8.99 f 0.17. This line was used to estimate the equilibrium constant for addition of hydroxide, and thence of water, to some additional esters where only the rate constant was available. Rate constants for hydrolysis of methyl esters in aqueous solution at 25°C were calculated from literature data, correcting for the effect of other conditions as necessary. From the equilibrium constants for addition of water we could estimate the rate constants for uncatalyzed hydrolysis; for the cases where this rate constant has been measured, the agreement was satisfactory. For acid catalyzed hydrolysis the data permit a test of the two alternative mechanisms considered previously, namely specific acid catalysis and general acid catalysis with hydronium ion acting as a general acid. For esters the mechanism is clearly specific acid catalysis, but for aldehydes and ketones it appears very likely that the mechanism is general acid catalysis.J. PETER GUTHRIE et PATRICIA A. CULLIMORE. Can. J. Chem. 58, 1281 (1980). On a mesure les chaleurs d'hydrolyse des orthoesters trimethyliques des acides isobutyrique, propionique, benzoique, methoxyacetique, chloroacetique et cyanacttique en utilisant une solution aqueuse acide avec un cosolvant organique lorsque cela s'avkre necessaire; on a aussi mesure les chaleurs d'hydrolyse des esters correspondants en solution basique. On a mesure les solubilites ou les energies libresde transfertde la phase gazeuse a la solution aqueuse ce qui a permisde calculerles energies libres de formation des orthoesters aqueux et de calculer, au moyen de methodes publiees anterieurement, les energies libres de formation des hydrates covalents des esters et les changements d'energie libre d'hydratation de ces esters.On a calcule les constantes d'equilibre de la reaction d'addition de I'hydroxyde sur les esters en utilisant les valeurs approximatives du pKa. Les donnees sont en parfait accord avec I'equation appropriee de Marcus reliant la vitesse et les constantes d'equilibre avec une valeur de b = 8.99 f 0.17. Cette donnee est utiliste pour evaluer la constante d'equilibre de la reaction d'addition d'hydroxyde et pa...

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“…There are two ways to prepare compounds 2a and 3a , from neutral indazoles 1a -1 H and 1a -2 H , reacting with neutral formaldehyde ( Scheme 2 , a and d reactions) or with protonated formaldehyde ( Scheme 2 , b and e reactions), or from protonated indazole 1aH + ( Scheme 2 , c reaction). Obviously, the mechanism should involve protonated formaldehyde because it is a much weaker base (p K a = −4.2) 34 than indazoles ( 1a , 1.04; 1b , 0.24; 1c , −0.96; 1d , −0.97; 1e , −0.99). 35 Therefore, it is impossible to have a direct reaction between the indazolium cation and neutral or protonated formaldehyde ( Scheme 2 c reaction).…”

Section: Introductionmentioning

confidence: 99%

Study of the Addition Mechanism of 1H-Indazole and Its 4-, 5-, 6-, and 7-Nitro Derivatives to Formaldehyde in Aqueous Hydrochloric Acid Solutions

et al. 2022

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The reaction of NH -indazoles with formaldehyde in aqueous hydrochloric acid has been experimentally studied by solution and solid-state nuclear magnetic resonance (NMR) and crystallography. The mechanism of the formation of N 1 -CH 2 OH derivatives was determined. For the first time, 2-substituted derivatives have been characterized by multinuclear NMR. Theoretically, calculations with gauge-invariant atomic orbitals (GIAOs) at the Becke three-parameter (exchange) Lee–Yang–Parr B3LYP/6-311++G(d,p) level have provided a sound basis for the experimental observations. The first X-ray structures of four (1 H -indazol-1-yl)methanol derivatives are reported.

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The Basic Strength of Formaldehyde

Abstract: The pKa of protonated formaldehyde has been estimated as -4.2, using spectroscopic and kinetic data obtained in concentrated acid solutions.

Cited by 6 publications

References 0 publications

Uptake of Gas-Phase Formaldehyde by Aqueous Acid Surfaces

Uptake of Gas-Phase Formaldehyde by Aqueous Acid Surfaces

Effect of the acyl substituent on the equilibrium constant for hydration of esters

Study of the Addition Mechanism of 1H-Indazole and Its 4-, 5-, 6-, and 7-Nitro Derivatives to Formaldehyde in Aqueous Hydrochloric Acid Solutions

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