Formation of chloroform from methane and chlorine is an example of

Alkyl Halides Imagine that a pair of crystallizing dishes are placed on an overhead projector as shown in the figure below. An alkene is added to the dish in the upper-left corner of the projector and an alkane is added to the dish in the upper-right corner. A few drops of bromine dissolved in chloroform (CHCl 3) are then added to each of the crystallizing dishes. The characteristic red-orange color of bromine disappears the instant this reagent is added to the alkene in the upper-left corner as the Br 2 molecules add across the C=C double bond in the alkene. The other crystallizing dish picks up the characteristic color of a dilute solution of bromine because this reagent doesn't react with alkanes under normal conditions. If the crystallizing dish in the upper-right corner is moved into the center of the projector, however, the color of the bromine slowly disappears. This can be explained by noting that alkanes react with halogens at high temperatures or in the presence of light to form alkyl halides. The light source in an overhead projector is intense enough to initiate this reaction, although the reaction is still significantly slower than the addition of Br 2 to an alkene. The reaction between an alkane and one of the halogens (F 2, Cl 2, Br 2, or I 2) can be understood by turning to a simpler example. CH 4( g) + Cl 2( g) CH 3Cl( g) + HCl( g) This reaction has the following characteristic properties. • It doesn't take place in the dark or at low temperatures. • It oc...

\( \newcommand\) • • • • • Alkanes (the most basic of all organic compounds) undergo very few reactions. The two reactions of more importaces is combustion and halogenation, (i.e., substitution of a single hydrogen on the alkane for a single halogen) to form a haloalkane. The halogen reaction is very important in organic chemistry because it opens a gateway to further chemical reactions. Combustion Complete combustion (given sufficient oxygen) of any hydrocarbon produces carbon dioxide and water. It is quite important that you can write properly balanced equations for these reactions, because they often come up as a part of thermochemistry calculations. Some are easier than others. For example, with alkanes, the ones with an even number of carbon atoms are marginally harder than those with an odd number! Example \(\PageIndex\): Propane Combustion For example, with propane (C 3H 8), you can balance the carbons and hydrogens as you write the equation down. Your first draft would be: \[ C_3H_8 + O_2 \rightarrow 3CO_2 + 4H_2O\] Counting the oxygens leads directly to the final version: \[ C_3H_8 + 5O_2 \rightarrow 3CO_2 + 4H_2O\] Example \(\PageIndex + 13 O_2 \rightarrow 8CO_2 + 10 H_2O\] The hydrocarbons become harder to ignite as the molecules get bigger. This is because the bigger molecules don't vaporize so easily - the reaction is much better if the oxygen and the hydrocarbon are well mixed as gases. If the liquid is not very volatile, only those molecules on the surface c...

Multiple substitution in the methane and chlorine reaction MULTIPLE SUBSTITUTION IN THE METHANE AND CHLORINE REACTION Warning! We are just about to muddy the water quite considerably! Don't go on until you are sure that you understand the mechanism for the production of chloromethane - and are confident that you could write it in an exam. If you aren't sure about it, It would be worth checking your syllabus and past exam papers to see if you need to know about these further substitution reactions. The facts When a mixture of methane and chlorine is exposed to ultraviolet light - typically sunlight - a substitution reaction occurs and the organic product is chloromethane. CH 4+ Cl 2 CH 3Cl + HCl However, the reaction doesn't stop there, and all the hydrogens in the methane can in turn be replaced by chlorine atoms. That means that you could get any of chloromethane, dichloromethane, trichloromethane or tetrachloromethane. CH 4+ Cl 2 CH 3Cl + HCl CH 3Cl + Cl 2 CH 2Cl 2+ HCl CH 2Cl 2+ Cl 2 CHCl 3+ HCl CHCl 3+ Cl 2 CCl 4+ HCl You might think that you could control which product you got by the proportions of methane and chlorine you used, but it isn't as simple as that. If you use enough chlorine you will eventually get CCl 4, but any other proportions will always lead to a mixture of products. The mechanisms The formation of multiple substitution products like di-, tri- and tetrachloromethane can be explained in just the same sort of way as the formation of the original chloro...

Around the world, about seven million people die each year from air pollution. World Health Organization (WHO) has reported that 9 out of 10 people breathe air that exceeds the WHO guideline values for the concentration of pollutants. The highest exposure is observed in low and middle-income countries. Urbanization and industrialization have led to the formation of many new chemical pollutants. The list of such emerging pollutants (EP) in the atmosphere is ever increasing. The sources and health impacts caused by EPs are still not well understood due to various reasons such as the paucity of monitoring data and lack of efficient detection methodology. Consequently, regulatory standards are missing for many of the EPs. The detection of such pollutants is difficult due to their complex behavior and sources in the atmosphere. Chloroform (CHCl 3) is one such EP in air, which is categorized as 2B carcinogen (probable human carcinogen) by the United States Environmental Protection Agency (US-EPA). CHCl 3 gets readily absorbed in the human body, where 60–80% of the inhaled quantity is absorbed and gets distributed throughout the body. The concentration of CHCl 3 found in indoor air is 10 folds higher than the outdoor air. Despite serious health effects caused by CHCl 3, it is not frequently monitored and included in National Ambient Air Quality Standards (NAAQs) of different countries. To address the knowledge gap, an in-depth analysis of literature was conducted. The toxicity pr...