Reaction dynamics of S(3P) with 1,3-butadiene and isoprene: crossed-beam scattering, low-temperature flow experiments, and high-level electronic structure calculations
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Crossed-beam velocity map imaging, chirped-pulse mmWave spectroscopy, and automated electronic structure calculations are used to investigate the reaction of ground-state sulfur atoms with 1,3-butadiene and isoprene.Keywords:
Isoprene
Dynamics
1,3-Butadiene
Reaction dynamics
Abstract. Ambient surface level concentrations of isoprene (C5H8) were measured in the major forest regions located south of Shanghai, China. Because there is a large coverage of broad-leaved trees in this region, high concentrations of isoprene were measured, ranging from 1 to 6 ppbv. A regional dynamical/chemical model (WRF-Chem) is applied for studying the effect of such high concentrations of isoprene on the ozone production in the city of Shanghai. The evaluation of the model shows that the calculated isoprene concentrations agree with the measured concentrations when the measured isoprene concentrations are lower than 3 ppb, but underestimate the measurements when the measured values are higher than 3 ppb. Isoprene was underestimated only at sampling sites near large bamboo plantations, a high isoprene source, indicating the need to include geospatially resolved bamboo distributions in the biogenic emission model. The assessment of the impact of isoprene on ozone formation suggests that the concentrations of peroxy radicals (RO2) are significantly enhanced due to the oxidation of isoprene, with a maximum of 30 ppt. However, the enhancement of RO2 is confined to the forested regions. Because the concentrations of NOx were low in the forest regions, the ozone production due to the oxidation of isoprene (C5H8 + OH → → RO2 + NO → → O3) is low (less than 2–3 ppb h−1). The calculation further suggests that the oxidation of isoprene leads to the enhancement of carbonyls (such as formaldehyde and acetaldehyde) in the regions downwind of the forests, due to continuous oxidation of isoprene in the forest air. As a result, the concentrations of HO2 radical are enhanced, resulting from the photo-disassociation of formaldehyde and acetaldehyde. Because the enhancement of HO2 radical occurs in regions downwind of the forests, the enhancement of ozone production (6–8 ppb h−1) is higher than in the forest region, causing by higher anthropogenic emissions of NOx. This study suggests that the biogenic emissions in the major forests to the south of Shanghai have important impacts on the levels of ozone in the city, mainly due to the carbonyls produced by the continuous oxidation of isoprene in the forest air.
Isoprene
Atmospheric chemistry
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Claeys questions whether gaseous epoxydiol is formed from the oxidation of isoprene and whether it is relevant to the formation of isoprene-derived secondary organic aerosol (iSOA). We argue that the alternative mechanism she proposes for iSOA applies primarily to chamber studies with high isoprene and is not as important in the atmosphere, where isoprene concentrations are much lower.
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Organolithium initiators are used extensively in the polymerization of butadiene and isoprene, because of their solubility in a variety of solvents. It is well known that non-polar media lead to polymers having a high 1,4 chain unit structure, while polar solvents can exert a dramatic effect in producing a high proportion of 1,2 or 3,4 structures. However, recent work, using the most accurate available NMR spectroscopy, has also shown that, even in nonpolar media, the concentration of initiator and the presence of solvent can have a very significant effect on the cis-1,4/trans-1,4 ratio, without noticeably influencing the proportion of side-vinyl units. Thus, at very low initiator concentrations (∼10-5 M. ), and in the absence of any solvents, it is possible to attain a cis-1,4 content of 96% for polyisoprene and 86% for polybutadiene. These chain structures have not been found to be noticeably affected by temperature or extent of conversion.
Isoprene
1,3-Butadiene
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Abstract Isoprene is a colorless, volatile liquid that is soluble in most hydrocarbons, but is practically insoluble in water. The isoprene unit exists extensively in nature. It is found in terpenes, camphors, Vitamin A and K, chlorophyll and other compounds isolated from plants and animals. Isoprene is highly reactive and its reactions are similar to those of butadiene. Russia dominates the world in terms of high purity isoprene capacity, production, and consumption. A principal route for the production of isoprene is recovery from ethylene by‐products streams. High purity isoprene is used almost in its entirety to produce polyisoprene. Isoprene emissions play an dominant role in atmospheric chemistry.
Isoprene
Terpene
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Abstract. Ambient surface level concentrations of isoprene (C5H8) were measured in the major forest regions located south of Shanghai, China. Because there is a large coverage of broad-leaved trees in this region, high concentrations of isoprene were measured, ranging from 1 to 6 ppbv. A regional dynamical/chemical model (WRF-Chem) is applied for studying the effect of such high concentrations of isoprene on the ozone production in the city of Shanghai. The evaluation of the model shows that the calculated isoprene concentrations agree with the measured concentrations when the measured isoprene concentrations are lower than 3 ppb, but underestimate the measurements when the measured values are higher than 3 ppb. Isoprene was underestimated only at sampling sites near large bamboo plantations, a high isoprene source, indicating the need to include geospatially resolved bamboo distributions in the biogenic emission model. The assessment of the impact of isoprene on ozone formation suggests that the concentrations of peroxy radicals (RO2) are significantly enhanced due to the oxidation of isoprene, with a maximum of 30 ppt. However, the enhancement of RO2 is confined to the forested regions. Because the concentrations of NOx were low in the forest regions, the ozone production due to the oxidation of isoprene (C5H8 + OH →→ RO2 + NO →→ O3) is low (less than 2–3 ppb/h). The calculation further suggests that the oxidation of isoprene leads to the enhancement of carbonyls (such as formaldehyde and acetaldehyde) in the regions downwind of the forests, due to continuous oxidation of isoprene in the forest air. As a result, the concentrations of HO2 radical are enhanced, resulting from the photo-disassociation of formaldehyde and acetaldehyde. Because the enhancement of HO2 radical occurs in regions downwind of the forests, the enhancement of ozone production (6–8 ppb/h) is higher than in the forest region, causing by higher anthropogenic emissions of NOx. This study suggests that the biogenic emissions in the major forests to the south of Shanghai have important impacts on the levels of ozone in the city, mainly due to the carbonyls produced by the continuous oxidation of isoprene in the forest air.
Isoprene
Atmospheric chemistry
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Abstract By means of ozone degradation experiments it has been shown that the isoprene units in copolymers of isoprene and isobutylene unite in the 1,4 positions. This conclusion is based on negative evidence. Since no evidence was found that would indicate a tendency for the isoprene units to occur in sequences, it is concluded that one isoprene unit cannot exert any directing influence on another, as far as their relative positions along the polymer chain are concerned. The existence of such an influence would necessitate the assumption of unprecedented long-range forces. Hence, the isoprene units must enter the chain in a random manner.
Isoprene
Isobutylene
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Isoprene
1,3-Butadiene
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Isoprene is the most abundant biogenic volatile organic compound in the atmosphere. Till now, chromatography is the main detection method for isoprene, dependent on sophisticated instruments and complex operations. An UV-Vis spectrophotometric method based on the Diels–Alder (D-A) reaction was developed to detect isoprene in the atmosphere. The fast D-A reaction between the probe 4-phenyl−1,2,4-triazolin−3,5-dione (PTAD) and isoprene may cause absorbance decrease, which enable it to detect isoprene in solution at 118 nmol·L−1 level. Further, isoprene in air at the level of ppbv was detected using this method. Compared with chromatography this method has the advantages of low cost, fast and less dependence on instrument.
Isoprene
Absorbance
Volatile organic compound
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Abstract Isoprene was dimerised by lithium naphthalene to linear isoprene dimer, a mixture of 2,6‐dimethyl‐2,6‐octadiene and 2,7‐dimethyl‐2,6‐octadiene, in 80% yield.
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This paper mainly discussed the application of isoprene in fine chemicals.The dimerization of isoprene and techniques of the isoprene derivatives were presented.Some suggestions for the development of isoprene were given to the plants which produce isoprene with extraction-distillation
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