- Haloalkanes and haloarenes undergo various reactions with metals.
- These reactions involve the displacement of the halogen atom by the metal atom.
- Here, we will discuss the reaction of haloalkanes and haloarenes with different metals.
Reaction with Sodium (Na)
- Haloalkanes react with sodium to form an alkane and sodium halide.
- For example, 2-chloropropane reacts with sodium to form propane and sodium chloride:
CH3CHClCH3 + 2Na → CH3CH2CH3 + 2NaCl
- Similarly, haloarenes also react with sodium to form an arene and sodium halide.
Reaction with Magnesium (Mg)
- Haloalkanes react with magnesium in the presence of anhydrous ether (diethyl ether) to form Grignard reagents.
- Grignard reagents are important intermediates in organic synthesis.
- For example, ethyl bromide reacts with magnesium to form ethylmagnesium bromide:
C2H5Br + Mg → C2H5MgBr
- Grignard reagents can further react with carbonyl compounds, forming alcohols or carboxylic acids.
Reaction with Zinc (Zn)
- Haloalkanes react with zinc in the presence of dry ether to form organozinc compounds.
- These reactions are known as the Negishi coupling reactions.
- For example, bromobenzene reacts with zinc to form phenylzinc bromide:
C6H5Br + Zn → C6H5ZnBr
- Organozinc compounds can further react with various electrophiles, creating different organic products.
Reaction with Iron (Fe)
- Haloalkanes react with iron in the presence of ether to form alkyl iron complexes.
- These complexes are used as reagents in organic synthesis.
- For example, 1-bromobutane reacts with iron to form tert-butyliron(II) chloride:
CH3CH2CH2CH2Br + Fe → (CH3)3CFeCl
- Alkyl iron complexes can undergo various reactions, such as oxidative addition or substitution.
Reaction with Silver (Ag)
- Haloalkanes react with silver in the presence of ammonia to form a complex called silver halide complex.
- This complex is soluble in ammonia.
- For example, bromoethane reacts with silver in the presence of ammonia to form silver bromide complex:
C2H5Br + Ag + 2NH3 → [Ag(NH3)2]Br
- This reaction is used in the analytical determination of halides.
- Reaction with Copper (Cu)
- Haloalkanes and haloarenes do not react directly with copper.
- However, they can react with copper in the presence of a catalyst to form copper(I) species.
- For example, bromoethane reacts with copper in the presence of a reducing agent to form ethyl copper:
C2H5Br + 2Cu + 2Li → C2H5Cu + 2LiBr
- Copper(I) species can further react with various electrophiles, resulting in the formation of different organic products.
- Reaction with Lithium (Li)
- Haloalkanes react with lithium in the presence of anhydrous ether (diethyl ether) to form organolithium compounds.
- Organolithium compounds are strong bases and nucleophiles.
- For example, 1-bromopropane reacts with lithium to form n-propyllithium:
CH3CH2CH2Br + 2Li → CH3CH2CH2Li + LiBr
- Organolithium compounds can undergo various reactions, such as nucleophilic substitution or addition.
- Reaction with Potassium (K)
- Haloalkanes react with potassium to form organopotassium compounds.
- Organopotassium compounds are strong bases and nucleophiles, similar to organolithium compounds.
- For example, 1-iodobutane reacts with potassium to form n-butyllithium:
CH3CH2CH2CH2I + 2K → CH3CH2CH2CH2K + KI
- Organopotassium compounds can also undergo nucleophilic substitution or addition reactions.
- Reaction with Aluminum (Al)
- Haloalkanes react with aluminum in the presence of ether to form alkyl aluminum compounds.
- These compounds are known as alkylaluminums or aluminum alkyls.
- For example, ethyl bromide reacts with aluminum to form triethylaluminum:
C2H5Br + Al → (C2H5)3Al
- Alkylaluminums can further react with various electrophiles, yielding diverse organic products.
- Reaction with Gold (Au)
- Haloalkanes do not react directly with gold.
- However, they can react with gold in the presence of a catalyst to form organogold complexes.
- For example, chloroethane reacts with gold in the presence of a silver catalyst to form ethyl gold(I) chloride:
C2H5Cl + Au + Ag → C2H5AuCl + AgCl
- Organogold complexes can undergo various reactions, including substitution or insertion processes.
- Reaction with Platinum (Pt)
- Haloalkanes and haloarenes do not react directly with platinum.
- However, they can react with platinum in the presence of a catalyst to form organoplatinum complexes.
- For example, bromobenzene reacts with platinum in the presence of tin(II) chloride to form phenylplatinum(II) chloride:
C6H5Br + Pt + SnCl2 → C6H5PtCl + SnCl4
- Organoplatinum complexes can participate in a range of reactions, such as oxidative addition, migratory insertion, or ligand exchange.
- Reaction with Mercury (Hg)
- Haloalkanes react with mercury in the presence of an acid catalyst to form organomercury compounds.
- Organomercury compounds are less common due to their high toxicity.
- For example, bromoethane reacts with mercury in the presence of hydrochloric acid to form ethylmercury chloride:
C2H5Br + Hg + HCl → C2H5HgCl + HBr
- Organomercury compounds can undergo various reactions, but their use is restricted due to their adverse effects on health and the environment.
- Reaction with Nickel (Ni)
- Haloalkanes and haloarenes do not react directly with nickel.
- But they can react with nickel in the presence of a catalyst to form organonickel complexes.
- For example, bromobenzene reacts with nickel in the presence of triethylamine to form phenylnickel(II) bromide:
C6H5Br + Ni + (C2H5)3N → C6H5NiBr + (C2H5)3NHBr
- Organonickel complexes can participate in various reactions, such as oxidative addition, reductive elimination, or migratory insertion.
- Reaction with Palladium (Pd)
- Haloalkanes and haloarenes do not react directly with palladium.
- However, they can react with palladium in the presence of a catalyst to form organopalladium complexes.
- For example, 2-bromopropane reacts with palladium in the presence of triphenylphosphine to form isopropylpalladium bromide:
(CH3)2CHBr + Pd + PPh3 → (CH3)2CHPdBr + PPh3Br
- Organopalladium complexes can participate in various reactions, including oxidative addition, reductive elimination, or cross-coupling reactions.
- Summary
- Haloalkanes and haloarenes can undergo different reactions with metals.
- These reactions involve the displacement of the halogen atom by the metal atom.
- Reactions with metals include the formation of alkyl or aryl metal compounds.
- Some important metal reactions include those with sodium, magnesium, zinc, iron, copper, lithium, potassium, aluminum, gold, platinum, mercury, nickel, and palladium.
- Reaction with Sodium (Na)
- Haloalkanes react with sodium to form an alkane and sodium halide.
- Example: 2-Chloropropane + Sodium → Propane + Sodium Chloride.
- Reaction with Magnesium (Mg)
- Haloalkanes react with magnesium in the presence of anhydrous ether.
- This forms Grignard reagents, which are important intermediates in organic synthesis.
- Example: Ethyl Bromide + Magnesium → Ethylmagnesium Bromide.
- Reaction with Zinc (Zn)
- Haloalkanes react with zinc in the presence of dry ether to form organozinc compounds.
- This reaction is called the Negishi coupling reaction.
- Example: Bromobenzene + Zinc → Phenylzinc Bromide.
- Reaction with Iron (Fe)
- Haloalkanes react with iron in the presence of ether to form alkyl iron complexes.
- These complexes are used as reagents in organic synthesis.
- Example: 1-Bromobutane + Iron → tert-Butyliron(II) Chloride.
- Reaction with Silver (Ag)
- Haloalkanes react with silver in the presence of ammonia to form a soluble silver halide complex.
- Example: Bromoethane + Silver + Ammonia → [Ag(NH3)2]Br.
- Reaction with Copper (Cu)
- Haloalkanes and haloarenes can react with copper in the presence of a catalyst.
- This leads to the formation of copper(I) species, which can react with electrophiles.
- Example: Bromoethane + Copper + Reducing Agent → Ethyl Copper.
- Reaction with Lithium (Li)
- Haloalkanes react with lithium in the presence of anhydrous ether to form organolithium compounds.
- Organolithium compounds are strong bases and nucleophiles.
- Example: 1-Bromopropane + Lithium → n-Propylithium.
- Reaction with Potassium (K)
- Haloalkanes react with potassium to form organopotassium compounds.
- These compounds are strong bases and nucleophiles.
- Example: 1-Iodobutane + Potassium → n-Butyllithium.
- Reaction with Aluminum (Al)
- Haloalkanes react with aluminum in the presence of ether to form alkyl aluminum compounds.
- Example: Ethyl Bromide + Aluminum → Triethylaluminum.
- Reaction with Gold (Au)
- Haloalkanes can react with gold in the presence of a catalyst to form organogold complexes.
- Example: Chloroethane + Gold + Silver catalyst → Ethyl Gold(I) Chloride.