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For aliphatic carbon-halogen bonds, the C-F bond is the strongest and usually less chemically reactive than aliphatic C-H bonds. The other aliphatic-halogen bonds are weaker, their reactivity increasing down the periodic table. They are usually more chemically reactive than aliphatic C-H bonds.
Haloalkanes containing halogens other than fluorine are more reactive than the parent alkanes—it is this reactivity that is the basis of most controversies. Many are alkylating agents , with primary haloalkanes and those containing heavier halogens being the most active (fluoroalkanes do not act as alkylating agents under normal conditions).
4 HCl + 2 CH 2 =CH 2 + O 2 → 2 Cl−CH 2 −CH 2 −Cl + 2 H 2 O Structure of a bromonium ion. The addition of halogens to alkenes proceeds via intermediate halonium ions. In special cases, such intermediates have been isolated. [5] Bromination is more selective than chlorination because the reaction is less exothermic.
Substitution reactions in organic chemistry are classified either as electrophilic or nucleophilic depending upon the reagent involved, whether a reactive intermediate involved in the reaction is a carbocation, a carbanion or a free radical, and whether the substrate is aliphatic or aromatic. Detailed understanding of a reaction type helps to ...
However, in basic solutions, successive halogenation is more rapid due to inductive electron withdrawal by the halogen. This makes the remaining hydrogens more acidic. In the case of methyl ketones , this reaction often occurs a third time to form a ketone trihalide, which can undergo rapid substitution with water to form a carboxylate ( −C ...
2 Na (s) + 2 H 2 O (l) →2 NaOH (aq) + H 2 (g) Metals in the middle of the reactivity series, such as iron, will react with acids such as sulfuric acid (but not water at normal temperatures) to give hydrogen and a metal salt, such as iron(II) sulfate: Fe (s) + H 2 SO 4 (l) → FeSO 4 (aq) + H 2 (g) There is some ambiguity at the borderlines ...
By the same token, however, since iodine has the lowest ionisation energy among the halogens and is the most easily oxidised of them, it has a more significant cationic chemistry and its higher oxidation states are rather more stable than those of bromine and chlorine, for example in iodine heptafluoride. [1]
A few types of aromatic compounds, such as phenol, will react without a catalyst, but for typical benzene derivatives with less reactive substrates, a Lewis acid is required as a catalyst. Typical Lewis acid catalysts include AlCl 3, FeCl 3, FeBr 3 and ZnCl 2. These work by forming a highly electrophilic complex which is attacked by the benzene ...