Halogens & Alkanes
2 guided lessons · 18 checks · 4. Organic Chemistry → Alkanes
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Swapping atoms under UV light
Left alone, an alkane ignores a halogen. Switch on ultraviolet light and a hydrogen atom is swapped for a halogen atom in a reaction whose shape this lesson maps out.
What you know already
From Alkanes you already know this family is generally unreactive, with halogen chemistry listed as one of its few moves. This note runs that move in detail: what ultraviolet light unlocks, the equations for methane with bromine and chlorine, and the halogenoalkane products that follow.
Key points of understanding
- A substitution reaction swaps one atom in a molecule for another atom.
- Alkanes react with halogens only in the presence of ultraviolet radiation.
- Methane plus bromine under UV gives bromomethane and hydrogen bromide: CH4 + Br2 -> CH3Br + HBr.
- The same pattern with chlorine gives chloromethane and hydrogen chloride: CH4 + Cl2 -> CH3Cl + HCl.
- The substitution here is limited to mono-substitution, one halogen atom per methane molecule.
In the presence of ultraviolet (UV) radiation, methane reacts with bromine in a substitution reaction
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1.Swapping atoms under UV light
Left alone, an alkane ignores a halogen. Switch on ultraviolet light and a hydrogen atom is swapped for a halogen atom in a reaction whose shape this lesson maps out.
In the presence of ultraviolet (UV) radiation, methane reacts with bromine in a substitution reaction
Key points
- A substitution reaction swaps one atom in a molecule for another atom.
- Alkanes react with halogens only in the presence of ultraviolet radiation.
- Methane plus bromine under UV gives bromomethane and hydrogen bromide: CH4 + Br2 -> CH3Br + HBr.
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