Basicity and acidity promote hydrolysis of methyl nitrate in aqueous aerosols

2020 ◽  
Author(s):  
Fatemeh Keshavarz ◽  
Theo Kurtén ◽  
Hanna Vehkamäki
Keyword(s):  
Nitric Acid ◽  
Nitrous Acid ◽  
Rate Coefficients ◽  
Alkyl Nitrates ◽  
Hydronium Ions ◽  
Hydroxyl Ion ◽  
Solvent Model ◽  
Methyl Nitrate ◽  
Hydrolysis Of ◽  
Aqueous Aerosols

<p>The chemistry of organic nitrates (ONs), also known as alkyl nitrates (RONO<sub>2</sub>), controls the lifetime of nitrogen oxides in continental areas, which in turn affects air quality and varies ozone concentration throughout the troposphere. ONs can be emitted to the troposphere from marine sources. Also, they can be produced in the atmosphere through addition of NO to peroxy radicals or through the reaction of NO<sub>3</sub> radicals with volatile organic compounds. Atmospheric ONs may subsequently undergo oxidation or photolysis, in both gas and aerosol phases, or hydrolysis in aqueous aerosols. Though some recent studies have believed acid-catalysis promotes hydrolysis of ONs, earlier studies have claimed that acids have no effect on ON hydrolysis, and that it is the hydroxyl ion that can improve the hydrolysis process. The limited number of experimental studies performed so far have left this conflict with no appropriate answer, as mechanistic insight and full kinetics details have been partially or completely missing for the studied ONs. We report the detailed mechanism of methyl nitrate hydrolysis in acidic, neutral and basic conditions, in addition to analyzing the degradation of methyl nitrate into formaldehyde and nitrous acid in the presence of water and hydronium ions. According to the potential energy surfaces obtained at the CCSD(T)/cc-pVDZ//ωB97X-D/def2-TZVP level of theory (including the SMD solvent model) along with the rate coefficients estimated using asymmetric Eckart tunneling-corrected transition state theory (TST), mediation of water molecules and hydronium ions hinders degradation of methyl nitrate into formaldehyde and nitrous acid and, in general, this decomposition reaction is kinetically unfavorable. Furthermore, neutral hydrolysis of methyl nitrate is extremely slow with pseudo-first order rate coefficients (k; 298 K and 1 atm) falling below 10<sup>-27</sup> s<sup>-1</sup>. Similarly, hydrolysis of methyl nitrate by hydronium ions is observed to be extremely slow (k < 10<sup>-27</sup> s<sup>-1</sup>). However, under acidic conditions, protonation of methyl nitrate is quite feasible with the protonation Gibbs free energy of -429.1 kJ mol<sup>-1</sup>, at 298 K and 1 atm, and protonated methyl nitrate can hydrolyze into protonated methanol and nitric acid much faster relative to the hydronium ion-based and neutral hydrolysis (k = 3.83 s<sup>-1</sup>). On the other hand, the hydroxyl ions generated under basic conditions can hydrolyze methyl nitrate readily to give methanol and nitric acid (k = 6.63 × 10<sup>3</sup> s<sup>-1</sup>), or formaldehyde, nitrate and water (k = 9.40 × 10<sup>6</sup> s<sup>-1</sup>). In addition, regardless of the limitation on the rate of solvent-phase chemical reactions by the rate of diffusion, basic hydrolysis can produce methoxy ions and nitric acid quite fast (k = 8.95 × 10<sup>9</sup> s<sup>-1</sup>). In other words, methyl nitrate hydrolysis is faster in basic aerosols (i.e. some marine aerosols) and, to a less extent, in highly acidic aqueous aerosols (e.g. haze and urban aerosols).       </p>

scholarly journals IX. The electric conductivity of nitric acid

1898 ◽  
Vol 191 ◽  
pp. 365-398 ◽  
Keyword(s):  
Nitric Acid ◽  
Physical Properties ◽  
Nitrous Acid ◽  
Internal Resistance ◽  
The Other ◽  
Reasonable Degree ◽  
Mineral Acids ◽  
Artificial Illumination ◽  
The Subject ◽  
Deep Green

Of the commoner mineral acids the chemical changes of Nitric Acid, from their evident complexity, have formed the subject of numerous memoirs, while those of sulphuric acid, from their assumed simplicity, have been to some degree neglected; on the other hand, the physical properties of the latter have been studied with considerable elaboration, while those of the former have been passed over, doubtless on account of the corrosive nature of the acid and the difficulty of preparing and preserving it in a reasonable degree of purity. Further, with certain exceptions, the alterations in physical properties induced by the products of reduction, be they nitrogen peroxide or nitrous acid, either singly or conjointly, have attracted but little attention, though it is a common matter of observation that the current intensity of a Grove’s or other cell containing nitric acid remains constant, even though the fuming acid, originally colourless or red, has become of a deep green tint. It is more than probable that of the factors of Ohm’s law, both the E. M. F. and internal resistance are continually varying. At the earliest stages of the enquiry it was found that the passage of a few bubbles of nitric oxide gas into a considerable volume of nitric acid produced an alteration of one percent, in the resistance, and the same result could be effected to a less degree by exposure to sunlight, and to a still less degree by exposure to artificial illumination. Therefore, we determined to investigate the alterations of conductivity produced by changes of concentration and temperature in samples of acid purified with necessary precautions, more especially as former workers upon the subject have either used samples of acid confessedly impure, or have been silent as to any method of purification, or have adopted no special care in dealing with a substance so susceptible of polarisation.

Spectrophotometric Method for the Microdetermination of Bendiocarb Standard Residues in Water

1988 ◽  
Vol 71 (1) ◽  
pp. 51-52
Author(s):  
Swadesh K Handa
Keyword(s):  
Nitric Acid ◽  
Spectrophotometric Method ◽  
Hydrolysis Of

Abstract A spectrophotometric method has been developed for the microdetermination of bendiocarb in water. The method is based on the reaction of bendiocarb phenol resulting from the hydrolysis of bendiocarb with nitric acid to form a yellow complex with an adsorption maximum at 420 nm. The method is applicable for estimation of residues of bendiocarb in the range of 10-100 μg/5 mL solution.

scholarly journals PRODUCTION OF CETANE IMPROVER FROM Jathropa curcas OIL

2010 ◽  
Vol 10 (3) ◽  
pp. 396-400 ◽  
Author(s):  
Abdullah Abdullah ◽  
D.R. Wicakso ◽  
A.B. Junaidi ◽  
Badruzsaufari Badruzsaufari
Keyword(s):  
Nitric Acid ◽  
Reaction Time ◽  
Sulphuric Acid ◽  
Jatropha Curcas ◽  
Cetane Number ◽  
Ftir Spectra ◽  
Alkyl Nitrates ◽  
Total N ◽  
Jatropha Curcas Oil ◽  
Magnetic Stirrer

Nitration of biodiesel from Jatropha curcas oil using mixture of HNO3 and H2SO4 had been done in an attempt to obtain a cetane improver or cetane number enhancer. The nitration was carried out by varying the numbers of moles of sulphuric acid, nitric acid, temperature and time. The process was conducted in a round bottom flask reactor that equipped with a magnetic stirrer and a ball cooler on a water batch. The mixture of H2SO4 and HNO3 was placed in the reactor and subsequently added slowly with biodiesel drop by drop. The results showed that increasing the mole numbers of sulphuric acid tends to reduce the yield or volume and total N of nitrated biodiesel. Increasing the number of moles of nitric acid tends to increase the yield, but decrease the value of total N. While increasing of temperature and reaction time tends to reduce the yield and total N. From FTIR spectra product was estimated as a mixture of esters of alkyl nitrates and nitro. From the testing of cetane number it can be predicted that nitrated biodiesel potentially as cetane improver.

THE ACID HYDROLYSIS OF GLYCOSIDES: I. GENERAL CONDITIONS AND THE EFFECT OF THE NATURE OF THE AGLYCONE

1964 ◽  
Vol 42 (6) ◽  
pp. 1456-1472 ◽  
Author(s):  
T. E. Timell
Keyword(s):  
Acid Hydrolysis ◽  
Equilibrium Concentration ◽  
Rate Coefficients ◽  
Acidity Function ◽  
Tertiary Alcohols ◽  
Conjugate Acid ◽  
Rate Of Hydrolysis ◽  
Acid Catalyzed ◽  
Opposing Effects ◽  
Hydrolysis Of

First-order rate coefficients and energies and entropies of activation have been determined for the acid-catalyzed hydrolysis of a number of methyl D-glycopyranosides and disaccharides. The relation between the logarithm of the rate coefficients and values for Hammett's acidity function was linear, although different for different acids. All compounds had entropies of activation indicating a unimolecular reaction mechanism. Glucosides of tertiary alcohols were hydrolyzed very rapidly, triethylmethyl β-D-glucopyranoside, for example, 30,000 times taster than the corresponding methyl compound.Increase in size of the aglycone caused a slight increase in the rate of hydrolysis of β-D-glucopyranosides, steric hindrance thus being of no significance. Electron-attracting substituents in the aglycone had little or no influence on the rate of hydrolysis, obviously because they would tend to lower the equilibrium concentration of the conjugate acid, while facilitating the subsequent heterolysis, the two opposing effects more or less cancelling out. These results were discussed in connection with recent studies on the acid hydrolysis of various phenyl glycopyranosides and with reference to the postulated occurrence of an activating inductive effect in oligo- and poly-saccharides containing carboxyl or other electronegative groups at C-5. It was concluded that there is little evidence for the existence of any such effect and that, for example, pseudoaldobiouronic acids should be hydrolyzed at the same rate as corresponding neutral disaccharides.

Methyl and ethyl nitrate saturation anomalies in the Southern Ocean (36 - 65°S, 30 - 70°W)

2008 ◽  
Vol 5 (1) ◽  
pp. 11 ◽  
Author(s):  
Claire Hughes ◽  
Adele L. Chuck ◽  
Suzanne M. Turner ◽  
Peter S. Liss
Keyword(s):  
Southern Ocean ◽  
Common Source ◽  
Alkyl Nitrates ◽  
Austral Spring ◽  
Study Region ◽  
Mixing Ratios ◽  
Alkyl Nitrate ◽  
Equatorial Ocean ◽  
Methyl Nitrate ◽  
Odd Nitrogen

Environmental Context. The alkyl nitrates are a group of organic compounds that are known to be produced naturally in seawater. The sea-to-air flux of alkyl nitrates is believed to contribute significantly to the ‘odd nitrogen’ reservoir of the atmosphere and to play an important role in regulating tropospheric ozone levels in remote marine regions. Here we expand our knowledge of alkyl nitrate concentration distributions and saturation anomalies to Southern Ocean waters. Abstract. We report the first coupled atmosphere and seawater alkyl nitrate measurements for the Southern Ocean in the area bounded by 36–65°S, 30–70°W (November/December, 2004). Methyl and ethyl nitrate concentrations in seawater were 3.1–194.9 and 0.3–71.8 pmol L–1, respectively. Atmospheric mixing ratios ranged from 1.0 to 71.5 ppt for methyl nitrate and 0.6 to 16.6 ppt for ethyl nitrate. No correlations between alkyl nitrate distributions, and sea surface temperature, windspeed or chlorophyll a were observed. However, methyl and ethyl nitrate were well correlated in both the air and seawater, which suggests a common source. Calculations based on these observations estimate median saturation anomalies of –40% (–95 to 220%) for methyl nitrate and –11% (–98 to 174%) for ethyl nitrate. Positive saturation anomalies were spatially patchy, which suggests that some methyl and ethyl nitrate production was taking place in isolated areas of the study region. Overall our negative median saturation anomaly values suggest that during late austral spring (2004) the region of the Southern Ocean in which our measurements were made was not a net source of methyl or ethyl nitrate to the atmosphere. These results reinforce previous findings which suggest that whilst the equatorial ocean is a major source of methyl and ethyl nitrates to the atmosphere, higher latitude waters are generally at equilibrium or under-saturated. More measurements are required to assess how representative our results are of other areas of the Southern Ocean.

Coupling between the Tropospheric Photochemistry of Nitrous Acid (HONO) and Nitric Acid (HNO3)

2006 ◽  
Vol 3 (1) ◽  
pp. 31 ◽  
Author(s):  
Kevin C. Clemitshaw
Keyword(s):  
Nitric Acid ◽  
Hydroxyl Radicals ◽  
Nitrous Acid ◽  
Snow Pack ◽  
Rural And Remote ◽  
Sources And Sinks ◽  
Tropospheric Photochemistry ◽  
Recent Developments ◽  
Urban Rural ◽  
And Migration

Environmental Context.Nitrous acid (HONO) is formed in the troposphere in urban, rural and remote environments via several uncertain heterogeneous and photochemical processes that involve nitric acid (HNO3). A recently recognised process is initiated by the deposition and migration of HNO3 within snow-pack surfaces to form nitrate anions (NO3−). Photo-reduction of NO3− followed by acidification of the nitrite (NO2−) photo-product leads to emissions of gas-phase HONO. Seasonal observations at Halley, Antarctica are consistent with the formation of HONO via this process, which is potentially of global significance because much of the Earth’s land (and sea) surface is covered with snow and is sunlit for much of the year. Both HONO and HNO3 significantly influence the production of ozone (O3), which acts as a greenhouse gas in the troposphere, via their respective roles as a source of hydroxyl radicals (OH•) and as a sink for OH• and nitrogen dioxide (NO2). Abstract.The tropospheric photochemistry of nitrous acid (HONO) and its coupling with that of nitric acid (HNO3) in urban, rural and remote atmospheres are highlighted in terms of established and uncertain homogeneous and heterogeneous sources and sinks, together with known and potential effects and impacts. Observations made at Halley, Antarctica, via optical detection of an azo dye derivative of HONO are consistent with snow-pack photochemical production of HONO, which has potential significance for the production of hydroxyl radicals (OH•) and ozone (O3) on regional and global scales. Recent developments in measurement methods for HONO and HNO3 are also highlighted. It is now timely to conduct a formal intercomparison of the methods in order to evaluate and enhance their capabilities, and to validate the growing body of HONO and HNO3 data obtained in urban, rural and remote locations.

Can nitrous acid contribute to atmospheric new particle formation from nitric acid and water?

2020 ◽  
Vol 44 (36) ◽  
pp. 15625-15635
Author(s):  
Shuang Ni ◽  
Feng-Yang Bai ◽  
Xiu-Mei Pan
Keyword(s):  
Optical Properties ◽  
Nitric Acid ◽  
Temperature Dependence ◽  
Nitrous Acid ◽  
Intermolecular Forces ◽  
Particle Formation ◽  
New Particle Formation

The properties of (HNO3)(HONO)(H2O)n (n = 1–6) clusters are reported including thermodynamics, structures, temperature-dependence, intermolecular forces, optical properties, and evaporation rates.

Sign in / Sign up

Export Citation Format

Share Document