What is a halogenoalkane?

An alkane with one or more hydrogen atoms replaced by halogen atoms.


Halogenoalkanes can also be called haloalkanes.

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What is bond enthalpy?

Bond enthalpy is the energy required to break one mole of covalent bonds between two atoms in the gaseous state.

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State and explain the trend in bond enthalpy of the carbon-halogen bond as we descend group 7. 

As we descend group 7, the carbon-halogen bond enthalpy decreases.


This is because the atomic radius of the halogens increases which leads to a longer carbon-halogen bond and a weaker attraction of the shared pair of electrons in the bond to the halogen nucleus.

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Why are carbon-halogens bonds polar?

Because halogens are more electronegative than carbon, so they pull the shared electrons towards them, giving the carbon a partial positive charge.

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State and explain the trend in reactivity of halogenoalkanes.

The reactivity increases in the order: chloroalkanes < bromoalkanes < iodoalkanes. 


This is due to the decrease in bond enthalpy of the carbon halogen bond in the order C-Cl > C-Br > C-I.


The fastest rate of reaction occurs in iodoalkanes because the C-I bond is the weakest. 

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