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Interhalogens are typically more reactive than all diatomic halogen molecules except F 2 because interhalogen bonds are weaker. However, the chemical properties of interhalogens are still roughly the same as those of diatomic halogens. Many interhalogens consist of one or more atoms of fluorine bonding to a heavier halogen.
Halogens are so named due to their potential to form salts, and form many simple strong acids with hydrogen. Out of the four stable halogens, only fluorine and chlorine have reduction potentials higher than that of oxygen, allowing them to form hydrofluoric acid and hydrochloric acid directly through reaction with water. [17]
Aliphatic compounds can be saturated, joined by single bonds (), or unsaturated, with double bonds or triple bonds ().If other elements (heteroatoms) are bound to the carbon chain, the most common being oxygen, nitrogen, sulfur, and chlorine, it is no longer a hydrocarbon, and therefore no longer an aliphatic compound.
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. Illustrative of the bromination of an alkene is the route to the anesthetic halothane from trichloroethylene: [6]
Similarly, if an atom has a positive charge and is attached to a +I group its charge becomes 'de-amplified' and the molecule becomes more stable than if the I-effect was not taken into consideration. The explanation for the above is given by the fact that more charge on an atom decreases stability and less charge on an atom increases stability.
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]
Thermodynamically, a chemical reaction occurs because the products (taken as a group) are at a lower free energy than the reactants; the lower energy state is referred to as the "more stable state." Quantum chemistry provides the most in-depth and exact understanding of the reason this occurs.
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).