The dipole moment of chlorobenzene is lower than that of cyclohexyl chloride

The dipole moment of chlorobenzene is less than cyclohexyl chloride as in chloro benzene because C-Cl bond is sp 2 hybridised where as in cyclohexyl chloride the C-Cl bond is SP 3 Hybridised . Since sp 2 has more s character and more electronegative than sp 3. Also, In chlorobenzene resonance gives rise to partial double bond charcter to the carbon- halogen bond, making it stronger by reducing the polarity of the carbon -halogen bond. Hence, chlorobenzene is less polar than cyclohexyl chloride. Freon-12: The chlorofluorocarbon compounds of methane and ethane are collectively known as ferons. Dichloro difluoro methane (Freon 12) is the most common freons. It is manufactured from tetra-chloromethane by the action of antimony trifluoride in the presence of antimony pentafluoride. Uses: (a) It is used as a refrigerant (cooling agent) in refrigerators and air conditioners. (b) It is also used as a propellant in aerosols and foams to spray out deodorants, cleaners, hair sprays, shaving creams. (c) It is also used as insecticides. (ii) DDT (p, p’ - Dichlorodiphenyl trichloro ethane): Preparation: It is manufactured by the condensation of chlorobenzene with trichloro acetaldehyde (chloral) in the presence of sulphuric acid. Uses: (a) It is a powerful insecticide. It is highly stable and not easily decomposed. (b) It is used for killing insects and mosquitoes. (iii) Carbon tetrachloride (CCl 4) : Preparation: It is prepared industrially by chlorination of methane and by the action ...

In chlorobenzene, the chlorine atom is attached to hybridized carbon atom(more 's' character). In cyclohexyl chloride, the chlorine atom is attached to hybridized carbon atom (less's' character than hybridized carbon atom). Hence chlorobenzene is more electronegative than cyclohexyl chloride. Therefore, the density of electrons C-Cl bond at chlorine atom is less in chlorobenzene than cyclohexyl chloride. The density of electrons C-Cl bond at chlorine atom in chlorobenzene decreases due to the -R effect of the benzene ring which is not in cyclohexyl chloride. Due to this polarity of the C-Cl bond decreases and hence dipole moment of chlorobenzene is lower than cyclohexyl chloride.

(i) In chlorobenzene, the C atom of the C-Cl bond is s p 2 hybridized and has more s character and electronegativity. In cyclohexyl chloride, the C atom of the C-Cl bond is s p 3 hybridized, has less s character and less electronegative. Hence, the C-Cl bond in chlorobenzene is less polar than the C-Cl bond in cyclohexyl chloride. Also, in chlorobenzene, the lone pair of electron on the Cl atom is in resonance with a benzene ring. This gives partial double bond character to C-Cl bond and there is a decrease in the magnitude of partial negative charge on Cl atom. However, in cyclohexyl chloride, there is a C-Cl single bond. The dipole moment is a product of charge and distance. Also C-Cl bond with partial double bond character has lower bond length than with C-Cl single bond. Hence, chlorobenzene has lower dipole moment than cyclohexyl chloride. (ii) Inter-molecular attractive forces present in alkyl halides are dipole dipole interactions and in case of water molecules, intermolecular hydrogen bonds are present. When alkyl halides are added to water, the intermolecular attractive force present between an alkyl halide and water molecules are weaker than the forces that are already present between two alkyl halide molecules and two water molecules. Hence, alkyl halides are water-immiscible. (iii) Grignard reagents are highly reactive with moisture that is present in apparatus or starting materials. Hence, we should prepare Grignard reagents in the anhydrous condition.

Chlorine is more electronegative than carbon. This creates a positive charge on carbon linked to Cl in cyclohexyl chloride. In chlorobenzene the electrons on chlorine participate in resonance with the ring. This decreases separation of charges. Hence dipole moment of chlorobenzene is lower than that of cyclohexyl chloride.

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(i) s p 2-hybrid carbon in chlorobezene is more electronegative than a s p 3-hybrid carbon in cyclohexylchoride , due to greater s-character. Thus, C atom of chlorobenzene has less tendency to release electrons to Cl than carbon atom of cyclohexylchloride. As a result, C - Cl bond in chlorobenzene is less polar than in cyclohexylchloride. Further, due to delocalization of lone pairs of electrons of the Cl atom over the benzene ring, C-Cl bond in chlorobenzene acquires some double bond character while the C - Cl in cyclohexy! chloride is a pure single bond. ln other words, C-Cl bond in chlorobenzene is shorter than in cyclohexyl chloride. Since dipole moment is a product of charge and distance, therefore, chlorobenzene has lowar dipole moment than cyclohexylchloride due to lower magnitude of negative charge on the Cl atom and shorter C-Cl distance. (ii) Alkyl halides are polar molecules, therefore, their molecules are held together by dipole-dipole attraction. The molecules of H 2 O are hold together by H-bonds . Since the new forces of attraction between water and alkyl halide molecules are weaker than the forces of attraction already existing between alkyl halide-alkyl halide molecules and water-water molecules, therefore, alkyl halides are immiscible (not soluble) in water. Alkyl halide are neither able to form H-bonds with water nor are able to break the H-bounding network of water. (iii) Grignard reagents are very reactive. They react with moisture present in the appar...