Haloalkanes

Haloalkanes, popularly called alkyl halides, are a class of chemical compounds in which one or more hydrogen atoms have been substituted by a halogen atom (fluorine, chlorine, bromine, or iodine). The structural and functional properties of haloalkanes differ significantly from alkanes’ structural and physical properties. The structural variations are caused by replacing one or more hydrogen atoms with a halogen atom, as previously stated. Electronegativity, bond length, bond strength, and molecule size all seem to be elements that influence physical qualities.

Haloalkanes Meaning

Haloalkanes were organic chemical compounds in which one or even more hydrogen atoms from an alkane group were replaced with a halogen group (elements of group 17 such as chlorine, bromine, fluorine, iodine, etc.) Haloalkanes are saturated organic compounds in which the halogen atom is bonded to a single carbon atom, and then all chemical linkages are single bonds.

Haloalkanes and Haloarenes

Haloalkanes are a class of organic compounds made up of halogenated alkanes. Haloarenes are a type of creature made of aromatic compounds with one or more halogen atoms. The fundamental distinction between haloalkane and haloarenes seems to be that haloalkane is an aliphatic halogen molecule, whereas haloarene is an aromatic halogen compound.

Furthermore, haloalkanes lack aromatic rings, whereas haloarene does. Free radical halogenation can also be used to make haloalkanes from alkanes, alkenes and alkynes, alcohol to carboxylic acids, and so on. The Sandmeyer reaction and the natural fragrance of aromatic rings are the two most popular techniques to make haloarene. As a result, another significant distinction between haloalkane and haloarene exists.

Physical Properties of Haloalkanes?

The physical properties of haloalkanes are as follows:

• Haloalkanes are colourless and odourless.

• They are naturally hydrophobic.

• If the number of carbon atoms in both is the same, the boiling point of haloalkanes is higher than that of alkanes. The boiling point of haloalkanes rises as the number of halogens in the compound increases. This indicates that 1-Bromo-2-chloroethane can boil at a greater temperature than chloroethane. The atomic weight of halides scales with the boiling temperatures of haloalkanes. Fluoroalkanes, on the other hand, are an exception. Its boiling point is lower than that of its equivalent alkanes. Fluorine has lower polarizability than other elements. 2- methylpropane has a boiling point of -11.7°C, while 2- fluoropropane has -10°C. Boiling points of isomeric haloalkanes fall as branching rises. 1-bromobutane has a boiling point of 375K, whereas 2-bromopropane has a boiling point of 346K.

             CH3CH2CH2CH2Br   B.P. =375K       

• Haloalkanes have more excellent melting points than their alkane equivalents. The melting point of haloalkanes is greater than that of alkanes with the same amount of carbon atoms as haloalkanes. Fluoroalkanes, however, constitute an exception. They have a lower melting point than alkanes that are similar to them. Methane, for instance, has a melting point of -182.5 °C, while tetrafluoromethane has a melting point of -183.6 °C.

• Although haloalkanes are volatile, they are less so than alkanes. Since haloalkanes contain fewer C-H bonds than alkanes, they are more flammable.

• Because haloalkanes are polar, they act as solvents. They are superior to alkanes as solvents.

• While fluoroalkanes are the exception, haloalkanes are much more reactive than equivalent alkanes. The reactivity of halogens rises as their atomic weight increases.

• Bromo, iodo, and polyhaloalkanes are usually heavier than water. The number of halogen atoms, carbon atoms, and atomic weight of halogen atoms all enhance the density of haloalkanes.

• In water, haloalkanes are only moderately soluble.

Chemical Properties of Haloalkanes

Haloalkanes are highly reactive substances. Substitution, elimination, as well as reduction reactions, occur. They can also generate organometallic compounds when they react with certain metals. The polar character of the carbon halogen bond contributes to the haloalkanes’ reactivity.

As the vitality of the C-X bond weakens, the stability of alkyl halides falls. Because of their low stability, iodides usually release iodine and turn even brown violet in colour.

2R-I → R-R + I2

Due to the release of iodine, iodoform has antibacterial effects.

Environmental Effects

In commercial applications, these compounds are commonly used. On the other hand, Halocarbons have been linked to significant pollutants and poisons that harm the environment. For instance, CFC (chlorofluorocarbon) is a well-known contributor to ozone depletion in the atmosphere. Some other highly discussed fumigant, methyl bromide, has been linked to a slew of detrimental environmental effects. These compounds have consistently been a severe environmental threat due to their damaging impacts. Other compounds, such as methyl iodide, on the other hand, have no ozone-depleting effects. Moreover, the USEPA has classified the chemical as a non-ozone layer depletion (the United States Environmental Protection Agency).

Conclusion

Alkanes with one or even more halogen substituents were haloalkanes, also known as halogenoalkanes or alkyl halides. Even though the difference is not always made, they are a subset of the general class of halocarbons. Competitively, haloalkanes were frequently used. Flame retardants, fire extinguishants, refrigerants, propellants, solvents, or medications are all examples of their uses. Many halocarbons have already been found to be severe pollutants or poisons due to their widespread use in commerce. Chlorofluorocarbons, for instance, have been related to ozone depletion.