Haloalkanes and haloarenes important points – Haloalkanes and haloarenes are the organic compounds that contains halogen atoms attached to the carbon atoms. They have distinct physical and chemical properties due to presence of halogens. These compounds are generally nonpolar and have higher boiling points compared to the hydrocarbons.
Nucleophilic substitution reactions are common and can be seen in haloalkanes and haloarenes, where a nucleophile replaces halogen atom. The reactions can proceed via either SN1 (unimolecular) or SN2 (bimolecular) mechanisms. SN1 reactions involves the formation of a carbocation intermediate, while SN2 reactions occurs through a direct attack of nucleophile on the carbon atom.
Elimination reactions can also occur, where a base removes a hydrogen and a halogen atom from an adjacent carbon atom, resulting in formation of a double bond. Elimination reactions can proceed via either E1 (unimolecular) or E2 (bimolecular) mechanisms. E1 reactions involves the formation of a carbocation intermediate, while E2 reactions occurs through a concerted elimination process.
Haloalkanes and haloarenes important points , Haloalkanes and haloarenes important points , Haloalkanes and haloarenes important points , Haloalkanes and haloarenes important points , Haloalkanes and haloarenes important points
NCER Chemistry Class 12 Chapter 10 – 25 Haloalkanes and haloarenes important points
There are 25 important points on haloalkanes and haloarenes –
- Haloalkanes and haloarenes are the organic compounds that contains halogen atoms (such as chlorine, bromine, or iodine) attached to carbon atoms.
- The general formula for the haloalkanes is R-X, where R represents an alkyl group and X represents a halogen atom. In haloarenes, halogen is directly bonded to an aromatic ring.
- The presence of halogen atoms in the haloalkanes and haloarenes significantly affects their physical and chemical properties.
- Haloalkanes and haloarenes are generally nonpolar and have higher boiling points compared to their corresponding hydrocarbons due to the increased intermolecular forces caused by polarizable halogen atoms.
- The reactivity of haloalkanes and haloarenes is largely determined by nature of the halogen atom and the carbon-halogen bond.
- Halogens in haloalkanes and haloarenes can undergo various types of reactions, including the nucleophilic substitution, elimination, and oxidation reactions.
- Nucleophilic substitution reactions are commonly observed in case of haloalkanes and haloarenes, where a nucleophile replaces the halogen atom. The mechanism can be either SN1 (unimolecular) or SN2 (bimolecular).
- In SN1 reactions, the carbon-halogen bond breaks first, forming a carbocation intermediate, followed by attack of a nucleophile. SN1 reactions are favored in polar protic solvents and with bulky alkyl groups.
- In SN2 reactions, nucleophile attacks the carbon atom while carbon-halogen bond is breaking. SN2 reactions are favored in polar aprotic solvents and with primary alkyl groups.
- The reactivity of halogen atom in haloalkanes and haloarenes follows the order: I > Br > Cl > F. This trend is due to the decreasing bond strength and increasing the bond length as we move down the halogen group.
- Elimination reactions can occurs in haloalkanes and haloarenes, where a base removes a hydrogen and a halogen atom from an adjacent carbon atom, resulting in formation of a double bond. The mechanism can be either E1 (unimolecular) or E2 (bimolecular).
- E1 reactions proceed via formation of a carbocation intermediate, followed by elimination of a proton and a halide ion.
- E1 reactions are favored in the polar protic solvents and with bulky alkyl groups.
- E2 reactions involves the concerted elimination of a proton and a halide ion. E2 reactions are favored in the polar aprotic solvents and with primary or secondary alkyl groups.
- The reactivity of the haloalkanes and haloarenes in the elimination reactions follows the same trend as in nucleophilic substitution reactions (I > Br > Cl > F).
- Haloalkanes and haloarenes can undergo oxidation reactions to form the corresponding alcohols or carboxylic acids.
- The oxidation of haloalkanes to alcohols typically involves use of strong oxidizing agents such as potassium permanganate (KMnO4) or chromium(VI) reagents like chromic acid (H2CrO4).
- Haloarenes are generally resistant to the oxidation reactions due to the strong carbon-halogen bond.
- Haloalkanes and haloarenes can undergo the reduction reactions to form alkyl or aryl compounds with a lower oxidation state.
- The reduction of haloalkanes is often
achieved using the reducing agents like lithium aluminum hydride (LiAlH4) or sodium borohydride (NaBH4). - Haloalkanes and haloarenes can undergo the oxidation reactions to form alcohols or carboxylic acids, with haloalkanes being more readily oxidized than haloarenes.
- Reduction reactions can also be employed to convert the haloalkanes and haloarenes to alkyl or aryl compounds with lower oxidation states.
- The reactivity of haloalkanes and haloarenes is influenced by nature of the halogen atom and the carbon-halogen bond.
- SN1 reactions involve the formation of a carbocation intermediate, while SN2 reactions occur through a direct attack of the nucleophile on the carbon atom.
- E1 reactions involve the formation of a carbocation intermediate, while E2 reactions occur through a concerted elimination process.
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