Physical properties of Haloderivatives Physical properties of haloderivatives are different than those of the simple hydrocarbons. This is because the greater polarity as well as higher molecular mass as compared to the parent hydrocarbon causes the intermolecular forces of attraction dipole-dipole and van der Waals to be stronger in the halogen derivatives. The inflammability decreases with increasing halogen content. Reactions of Haloalkanes The reactions of haloalkanes may be divided into the three main categories: i Nucleophilic substitution ii Elimination reactions iii Reaction with metals Nucleophilic substitution: A nucleophile attacks the haloalkane which is having a partial positive charge on the carbon atom bonded to halogen. Halide ion separates following a substitution reaction.
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Numerous ways to make alkyl halides. Radical Halogenation: Selectivity If there is more than one type of hydrogen in an alkane, reactions favor replacing the hydrogen at the most highly substituted carbons. Relative Reactivity 1. Based on quantitative analysis of reaction products, relative reactivity is estimated for Cl2: Order parallels stability of radicals 3.
An allylic hydrogen has been substituted for a bromine. The bromine atom abstracts an allylic hydrogen because the allylic radical is resonance stabilized. The radical then reacts with a bromine molecule to continue the chain. They have the general formula ArX, where Ar is phenyl substituted phenyl or a group derived from some other aromatic system e. An aryl halide is not just any halogen compound containing an aromatic ring [C6H5 — CH2 — Cl] is not an aryl halide for the halogen is not attached to the benzene ring.
In Sandmeyer reaction, cuprous halides are used which are unstable and difficult to handle, however in Gattermann reaction copper power and a hydrogen halide are used. To get iodobenzene, HI must be removed from the reaction mixture. Structure and Reactivity of Aryl Halide and Vinyl Halides: Chlorobenzene is a resonance hybrid of 5 resonating structures.
Hence C-Cl bond in chlorobenzene is strong. As a result, aryl halides are less reactive compared to the corresponding alkyl halide towards nucleophilic substitution reaction. Similar is the case with vinyl halides. The sp2 hybridized carbon atom is more electronegative than the sp3 hybridized carbon atom, thereby the release of electrons to chlorine atoms is less in chlorobenzene and more in alkyl chloride.
Thus the benzene ring definitely takes part in electrophilic substitution reactions.
Haloalkanes And Haloarenes Notes Class 12
Numerous ways to make alkyl halides. Radical Halogenation: Selectivity If there is more than one type of hydrogen in an alkane, reactions favor replacing the hydrogen at the most highly substituted carbons. Relative Reactivity 1. Based on quantitative analysis of reaction products, relative reactivity is estimated for Cl2: Order parallels stability of radicals 3. An allylic hydrogen has been substituted for a bromine.
Haloalkanes and Haloarenes Class 12 Notes Chemistry Chapter 10
Chemical reactions of haloalkanes a Nucleophilic substitution reactions: i C-X bond in alkyl halide is more polar due to electron repelling nature of alkyl group - and thus readily undergo nucleophilic substitution reaction. Such reactions are favoured by polar solvents. Aryl halides are extremely less reactive towards nucleophilic substitution reaction due to following reasons: a In haloarenes, the lone pair of electrons on the halogen atom are delocalized on the benzene ring due to resonance. Electrophilic substitution reaction: Haloarenes undergo the usual electrophilic substitution reactions of the benzene ring such as halogenation, nitration, sulphonation and Friedel crafts reactions. Halogen atom is slightly deactivating and o, p-directing. Trichloromethane Chloroform : The major use of chloroform today is in the production of the freon refrigerant R Chloroform is stored in closed dark coloured bottles completely filled so that air is kept out Because it is slowly oxidised by air in the presence of light to an extremely poisonous gas, carbonyl chloride Phosgene.
CBSE Class 12th Chemistry Notes: Haloalkanes and Haloarenes (Part - I)