ChemInform Abstract: Radical Spectra and Product Distribution Following Electrophilic Attack by the OH· Radical on 4-Hydroxybenzoic Acid and Subsequent Oxidation.

Abstract. The ozonolysis of α-pinene has been investigated under dry and humid conditions in the temperature range of 243–303 K. The results provided new insight into the role of water and temperature in the degradation mechanism of α-pinene and in the formation of secondary organic aerosols (SOA). The SOA yields were higher at humid conditions than at dry conditions. The water induced gain was largest for the lowest temperatures investigated (243 and 253 K). The increase in the SOA yields was dominated by water (and temperature) effects on the organic product distribution, whilst physical uptake of water was negligible. This will be demonstrated for the example of pinonaldehyde (PA) which was formed as a major product in the humid experiments with total molar yields of 0.30±0.06 at 303 K and 0.15±0.03 at 243 K. In the dry experiments the molar yields of PA were only 0.07±0.02 at 303 K and 0.02±0.02 at 253 K. The observed partitioning of PA as a function of the SOA mass present at 303 K limited the effective vapour pressure of pure PA pPA0 to the range of 0.01–0.001 Pa, 3–4 orders of magnitude lower than literature values. The corresponding mass partitioning coefficient was determined to KPA=0.005±0.004 m3 μg−1 and the total mass yield αPAtotal=0.37±0.08. At 303 K PA preferably stayed in the gas-phase, whereas at 253 K and 243 K it exclusively partitioned into the particulate phase. PA could thus account at least for half of the water induced gain in SOA mass at 253 K. The corresponding effect was negligible at 303 K because the PA preferably remained in the gas-phase. The yield of OH radicals, which were produced in the ozonolysis, was indirectly determined by means of the yield of cyclohexanone formed in the reaction of OH radicals with cyclohexane. OH yields of the α-pinene ozonolysis were determined to 0.67±0.17 for humid and 0.54±0.13 for dry conditions at 303 K, indicating a water dependent path of OH radical formation. For 253 and 243 K OH yields could be estimated to 0.5 with no significant difference between the dry and humid experiments. This is the first clear indication for OH radical formation by α-pinene ozonolysis at such low temperatures.

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Influence of relative humidity and temperature on the production of pinonaldehyde and OH radicals from the ozonolysis of α-pinene

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-10-3129-2010 ◽

2010 ◽

Vol 10 (2) ◽

pp. 3129-3172 ◽

Cited By ~ 1

Author(s):

R. Tillmann ◽

M. Hallquist ◽

Å. M. Jonsson ◽

A. Kiendler-Scharr ◽

H. Saathoff ◽

...

Keyword(s):

Gas Phase ◽

Degradation Mechanism ◽

Product Distribution ◽

Major Product ◽

Radical Formation ◽

Oh Radicals ◽

Oh Radical ◽

Significant Difference ◽

Dry Conditions

Abstract. The ozonolysis of α-pinene has been investigated under dry and humid conditions in the temperature range of 243–303 K. The results provided new insight into the role of water and temperature in the degradation mechanism of α-pinene and in the formation of secondary organic aerosols (SOA). The SOA yields were higher at humid conditions than at dry conditions. The water induced gain was largest for the lowest temperatures investigated (243 and 253 K). The increase in the SOA yields was dominated by water (and temperature) effects on the organic product distribution, whilst physical uptake of water was negligible. This will be demonstrated for the example of pinonaldehyde (PA) which was formed as a~major product in the humid experiments with total molar yields of 0.30±0.06 at 303 K and 0.15±0.03 at 243 K. In the dry experiments the molar yields of PA were only 0.07±0.02 at 303 K and 0.02±0.02 at 253 K. The observed partitioning of PA as a function of the SOA mass present at 303 K limited the effective vapour pressure of pure PA pPA0 to the range of 0.01–0.001 Pa, 3–4 orders of magnitude lower than literature values. The corresponding mass partitioning coefficient was determined to KPA=0.005±0.004 m3/μg and the total mass yield αPA.total=0.37±0.08. At 303 K PA preferably stayed in the gas-phase, whereas at 253 K and 243 K it exclusively partitioned into the particulate phase. PA could thus account at least for half of the water induced gain in SOA mass at 253 K. The corresponding effect was negligible at 303 K because the PA preferably remained in the gas-phase. The yield of OH radicals, which were produced in the ozonolysis, was indirectly determined by means of the yield of cyclohexanone formed in the reaction of OH radicals with cyclohexane. OH yields of the α-pinene ozonolysis were determined to 0.67±0.17 for humid and 0.54±0.13 for dry conditions at 303 K, indicating a water dependent path of OH radical formation. For 253 and 243 K OH yields could be estimated to 0.5 with no significant difference between the dry and humid experiments. This is the first clear indication for OH radical formation by α-pinene ozonolysis at such low temperatures.

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γ-Radiolysis of 2′-Deoxycytidine-5′-phosphate in Deoxygenated Aqueous Solutions. OH Radical-Induced Alterations at the Sugar Moiety

Zeitschrift für Naturforschung B ◽

10.1515/znb-1983-1009 ◽

1983 ◽

Vol 38 (10) ◽

pp. 1213-1220 ◽

Cited By ~ 6

Author(s):

Heinz-Peter Schuchmann ◽

Rita Wagner ◽

Clemens von Sonntag

Keyword(s):

Aqueous Solutions ◽

Product Distribution ◽

Strand Break ◽

Model System ◽

Radical Reactions ◽

Oh Radical ◽

Free Sugars ◽

Sugar Moiety ◽

Related Compounds ◽

Break Formation

Abstract In order to elucidate some aspects of the mechanism of radical-induced strand break formation in DNA, the γ-radiolysis of N2O-saturated aqueous solutions of 2′-deoxycytidine-5′-phosphate has been studied as a model system. At pH 4 it has been observed that upon OH attack at the sugar moiety phosphate (G ≈ 0.6) and cytosine (G = 1) are released and the following cytosine-free sugars are formed: 2,5-dideoxypentos-3,4-diulose, 1 (G = O.22), 2-deoxy-pentos-4-ulose, 2 (G = 0.18), 2-deoxy-pentos-4-ulose-5-phosphate, 3 (G=0.06), 2-deoxypentonic acid-5-phosphate and its lactone, 5 (G ≈ 0.5). Some 2-deoxyribose-5-phosphate, 4 is also formed.Upon addition of H2O2 (up to 10-2 M) prior to irradiation, G(1) is drastically reduced without giving rise to another cytosine-free product. G(3) increases at the expense of G(2). G (4 + 5) also increase upon H2O2 addition. The formation of these products and the change of their G values as a function of H2O2 concentration are discussed in the light of well-documented radical reactions of carbohydrates and related compounds.The precursor of 1 has been considered to be the radical at C-3′, that of 2 and 3 the radical at C-4′ and that of 5 the radical at C-1′. Product 4 is thought to arise from a radical-induced destruction of the cytosine moiety. These primary radicals which may undergo rearrangement, or eliminate phosphate, are readily oxidised by H2O2, a reaction which leads to the change of product distribution mentioned above.

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Use of thermomechanical pulp fibers from waste woods for making eco-friendly cushioning material

TAPPI Journal ◽

10.32964/tj9.7.15 ◽

2010 ◽

Vol 9 (7) ◽

pp. 15-21 ◽

Cited By ~ 1

Author(s):

JI-YOUNG LEE ◽

CHUL-HWAN KIM ◽

JEONG-MIN SEO ◽

HO-KYUNG CHUNG ◽

KYUNG-KIL BACK ◽

...

Keyword(s):

Impact Test ◽

Product Distribution ◽

Expanded Polystyrene ◽

Thermomechanical Pulp ◽

Fiber Structure ◽

Pulp Fibers ◽

Cationic Starch ◽

Thermal Insulating ◽

Surface Sizing ◽

The Impact

Eco-friendly cushioning materials were made with thermomechanical pulps (TMPs) from waste woods collected from local mountains in Korea, using a suction-forming method without physical pressing. The TMP cushions had superior shock-absorbing performance, with lower elastic moduli than expanded polystyrene (EPS) or molded pulp. Even though the TMP cushions made using various suction times had many voids in their inner fiber structure, their apparent densities were a little higher than that of EPS and much lower than that of molded pulp. The addition of cationic starch contributed to an increase in the elastic modulus of the TMP cushions without increasing the apparent density, an effect which was different from that of surface sizing with starch. In the impact test, the TMP cushions showed a more ductile pattern than the brittle EPS. The porosity of the TMP cushion was a little less than that of EPS and much greater than that of molded pulp. The porous structure of the TMP cushions contributed to their excellent thermal insulating capacity, which was equivalent to that of EPS. In summary, the TMP packing cushions showed great potential for surviving external impacts during product distribution.

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Fiber Coupled Ultraviolet Planar Laser Induced Fluorescence of OH Radical

50th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition ◽

10.2514/6.2012-1059 ◽

2012 ◽

Author(s):

Frank Loccisano ◽

Azer Yalin ◽

Sachin Joshi ◽

Isiaha Franka ◽

Zhiyao Yin ◽

...

Keyword(s):

Laser Induced Fluorescence ◽

Oh Radical ◽

Planar Laser Induced Fluorescence ◽

Planar Laser

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An NBO-TS predictive approach for torquoselectivity of ring opening in 3-substituted cyclobutenes

10.26434/chemrxiv.5743305.v1 ◽

2017 ◽

Author(s):

Arpita Yadav ◽

Dasari L V K Prasad ◽

Veejendra Yadav

Keyword(s):

Transition State ◽

Ring Opening ◽

Natural Bond Orbital ◽

Theoretical Calculations ◽

Lone Pair ◽

Product Distribution ◽

Acceptor Substituent ◽

Important Contributor ◽

Predictive Approach ◽

Donor Substituent

The torquoselectivity, the inward or outward ring opening of 3-substituted cyclobutenes, is conventionally guided by the donor and/or acceptor ability of the substituent (S). It is typically predicted by estimating the respective ring opening transition state (TS) barriers. While there is no known dissent in regard to the outward rotation of electron-rich substituents from the approaches of TS calculations, the inward rotation was predicted for some electron-accepting substituents and outward for others. To address this divergence in predicting the torquoselectivity, we have used reliable orbital descriptors through natural bond orbital theoretical calculations and demonstrated that (a) interactions nS→s*C3C4 for a lone pair containing substituent, sS→s*C3C4 for a s-donor substituent, sC3C4→p*S for a resonance-accepting substituent and sC3C4→s*S for a s-acceptor substituent constitute the true electronic controls of torquoselectivity, and (b) reversibility of the ring opening event is an additional important contributor to the observed product distribution.

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