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Applied Chemistry and Physics
Published in Robert A. Burke, Applied Chemistry and Physics, 2020
Alkyl halide compounds can be found as liquids or gases. As a family the alkyl halides are toxic to varying degrees and some are flammable. Alkyl halides are composed of one of the hydrocarbon radicals with varying numbers and combinations of the halogen family of elements attached: fluorine (F), chlorine (Cl), bromine (Br) and iodine (I). The toxicity of the compound is derived from the halogens and the flammability from the hydrocarbons, specifically the hydrogen. The more halogens present the more toxic the compound; the more hydrogens the more flammable they become. The simplest of the alkyl halides is formed from methane. One hydrogen atom is replaced by one chlorine atom forming the compound methyl chloride, also called chloromethane. Hydrocarbon is represented in the name as well as chlorine. Methyl chloride is a colorless compressed gas or liquid with an ether-like odor. Fire risk is significant with a flammable range of 10.7%–17% in air. Methyl chloride has narcotic effects, with a threshold limit value (TLV) of 50 ppm in air. Uses include a refrigerant, topical anesthetic, solvent and herbicide. Adding two more chlorines, it becomes trimethyl chloride, with the trade name of chloroform. Now the flammability is gone, but the toxicity has increased to 10 ppm in air.
Alkyl Halides and Substitution Reactions
Published in Michael B. Smith, A Q&A Approach to Organic Chemistry, 2020
An alkyl halide is any molecule that contains one or more halogen atoms attached to a carbon atom. In most cases, the carbon atom will be sp3-hybridized, but halogens can be attached to sp2- and also sp-hybridized carbon, so alkene halides and alkyne halides are known. Why is the C—X bond of an alkyl halide polarized?
Chemistry of Hydrocarbons
Published in Jimmy H.C. Wong, Chin Hong Lim, Greg L. Nolen, Design of Remediation Systems, 2020
Jimmy H.C. Wong, Chin Hong Lim, Greg L. Nolen
Alkyl halides are formed by the substitution of halogen atoms for one or more hydrogen atoms on alkanes. Examples include carbon tetrachloride (CCl4) and dichloromethane (CH2Cl2).
Effect of substitution on dissociation kinetics of C2H5X, (X = F, Cl, Br and I): A theoretical study
Published in Molecular Physics, 2021
Nitin R. Gulvi, Priyanka Patel, Parimal J. Maliekal, Purav M. Badani
The chemistry of halogenated hydrocarbons is proven to be a compelling case of study, for both industrial applications as well as its hazardous effects on the environment [1,2]. For instance, these compounds are profoundly used as refrigerants, aerosol sprays, anesthetics and blowing agents for foam packing [3]. However, the dissociation of these compounds generate reactive halogen species, which shows catalytic behaviour towards ozone depletion [4–7]. Furthermore, the reactivity is known to stringently depend upon the halogen atom that is present in the molecular frame. For instance, Goodall et al. [8] had reported the activation of molecular (HCl) elimination channel, upon thermal decomposition of allyl chloride. On the other hand, Maccoll et al. [9] and Maloney et al. [10] had observed the C–Br and C–I bond dissociation reactions to be the more dominant as compared to the counterpart molecular eliminations from allyl bromide and allyl iodide respectively. In addition to the substituent, pressure and temperature are also known to affect the dissociation kinetics. For example, Roy et al. [11] demonstrated that the pyrolysis of 2-bromopropene, in the pressure range of 150–800 kPa and temperature range of 1100–1250 K, results in the generation of HBr along with propyne or allene. They reported a branching ratio as 0.64 for the production of propyne with respect to allene. In another study, Nisar et al. [12] exploited the thermal decomposition of the same molecular system at 571–654 K and 12–46 Torr. They also observed propyne as the major product, but with a branching ratio of 0.98. Above literature, depicts that the decomposition of alkyl halide is altered with substituted halogen species, temperature and pressure.
Characterization of indoor settled dust and investigation of indoor air quality in different micro-environments
Published in International Journal of Environmental Health Research, 2018
Veerendra Sahu, Suresh Pandian Elumalai, Sneha Gautam, Nitin Kumar Singh, Pradyumn Singh
This paper presented the outcomes of a study on characterization of physico-chemical properties of settled dust particles in different micro-environment at a technical institution at Dhanbad – the coal capital of India, which are very important from the occupational health point of view. Physico-chemical characterization of indoor settled dust was performed using FESEM, EDX, and FTIR analysis. Most of the particles found in dust were soot, minerals, gypsum. Outdoor sample characterization results also confirmed the presence of these particles. Elemental analysis of settled dust samples collected from studied sites showed the presence of various elements such as C, O, Na, Mg, Al, Si, S, Cl, K, Ca, Fe, and Ti. The average content of O and C in dust samples was found about 42.7% and 18.9%, respectively. Presence of Alkyl Halide (C–F), Alkane (C–H), and other functional groups in FTIR spectra of these samples confirmed the presence of VOC in indoor dust. Monitoring results of PM10, and PM2.5 revealed that the particle concentration in all indoor environment exceeded the permissible limit of WHO guidelines. VOC, CO2, and humidity were found to be within the limits described by IAQ Index and ASHRAE. On the other side, temperature in all indoor environments exceeded the comfort condition limits described by ASHRAE guidelines. Moreover, particles are primarily occurring in accumulation mode as a function of relative humidity. Accumulation of fine particles is more dominant in winter time, which is a significant contributor in different micro-environments. The observed results of physiochemical characterization of fine particles clearly support the importance of IAQ standards especially for Indian region and may provide useful information for setting up the same.