Theoretical calculation of the reaction mechanism between ammonia and formaldehyde

Dimethylamine Addition to Formaldehyde Catalyzed by a Single Water Molecule: A Facile Route for Atmospheric Carbinolamine Formation and Potential Promoter of Aerosol Growth

“…Because of its potential astrophysical importance, the NH 3 + H 2 CO reaction catalyzed by water has been investigated by several groups. [1][2][3]5,6,8 We have also carried out calculations on the NH 3 + H 2 CO + H 2 O reaction, and our results, presented in the Supporting Information ( Figures 1S and 2S), are in line with the previous studies. We find that at the CCSD(T)/6-311++G(3df,3dp)//MP2/6-311++G(3df,3dp) level of theory, the barrier for the addition of ammonia to H 2 CO catalyzed by a single water molecule is 16.3 kcal/mol, in reasonable accord with previous calculations at the CCSD(T)/6-311+G**// MP2/6-311+G** level, which find the barrier to be 19.0 kcal/ mol.…”

“…13,15 Many studies have revealed the important role that amines play in the chemistry of the earth's atmosphere, especially in promoting aerosol growth. 12−35 Oxidation of amines via OH and NO 3 radicals, acid−base reactions of amines with H 2 SO 4 or HNO 3 , and formation of nitrosamines are a few examples of atmospheric amine chemistry that have thus far been studied. 11,14,33 The atmospheric chemistry of amines has been reviewed recently by Nielsen et al, who emphasized the need for additional kinetic and mechanistic data.…”

“…Amines are important compounds that are of interest to a wide range of researchers exploring such diverse areas as the formation of amino acids in interstellar space, − schemes for carbon capture, − and aerosol formation in the earth’s troposphere. − In the earth’s atmosphere, amines arise from both anthropogenic and biogenic sources including animal husbandry, automobile exhaust, marine organisms, and biomass burning. ,, The atmospheric removal of amines results from their reactions with either nitric or sulfuric acid to form the corresponding salts or through oxidation by OH, O 3 , and NO 3 . The concentrations of amines vary widely depending on location and proximity to the source with their ambient concentrations typically being at least an order of magnitude smaller than that of ammonia. , Many studies have revealed the important role that amines play in the chemistry of the earth’s atmosphere, especially in promoting aerosol growth. − Oxidation of amines via OH and NO 3 radicals, acid–base reactions of amines with H 2 SO 4 or HNO 3 , and formation of nitrosamines are a few examples of atmospheric amine chemistry that have thus far been studied. ,, The atmospheric chemistry of amines has been reviewed recently by Nielsen et al, who emphasized the need for additional kinetic and mechanistic data .…”

“…Because reaction is also potentially important as an astrophysical mechanism for spawning molecular complexity, several studies have discussed the energetics of reaction in the context of ammonia and/or methylamine reacting with formaldehyde on comets and interstellar ice. − Results of computational studies show that a single water molecule can significantly reduce the activation energy to carbinolamine formation for both the ammonia and methylamine addition reactions with formaldehyde; however, the barrier reduction is apparently not of sufficient degree to make the reactions occur readily under atmospheric conditions in the gas phase. ,,,, To the best of our knowledge, the corresponding reaction involving dimethylamine and formaldehyde has not been reported in the literature. Given that formaldehyde is the simplest and most abundant carbonyl compound in our atmosphere − and that dimethyamine has been observed in nanoparticles during atmospheric nucleation events and is known to stabilize sulfuric acid nanoparticles better than either ammonia or methylamine, ,,,,− the reaction of formaldehyde with dimethylamine can potentially be important in understanding the chemistry of aerosol growth.…”

Off-pathway 3D-structure provides protection against spontaneous Asn/Asp isomerization: shielding proteins Achilles heel

“…Thus it appears that beyond rigidity or flexibility, the specific arrangement of the reacting partners of the deamidation within a given fold should also be considered. The orientation and distance of the nucleophilic amide and its target C γ = O δ can be described using Bürgi-Dunitz (BD) distance (d ) and angle (θ) to track the isomerization path (Burgi et al, 1974;Ospina and Villaveces, 1993) (Fig. 5).…”