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Questions and Answers
Which of the following is the correct general formula for haloalkanes?
Which of the following is the correct general formula for haloalkanes?
- CₙH₂ₙX
- CₙH₂ₙ₋₂X
- CₙH₂ₙ₊₂X₂
- CₙH₂ₙ₊₁X (correct)
SN1 reactions are favored by primary haloalkanes due to less steric hindrance.
SN1 reactions are favored by primary haloalkanes due to less steric hindrance.
False (B)
Which of the following reagents is best suited for converting an alcohol to a haloalkane?
Which of the following reagents is best suited for converting an alcohol to a haloalkane?
- SOCl₂ (correct)
- Aqueous KOH
- KMnO₄
- H₂O, H₂SO₄
What is the IUPAC name for the compound with the structure CH₃-CH(Cl)-CH₂-CH₃?
What is the IUPAC name for the compound with the structure CH₃-CH(Cl)-CH₂-CH₃?
The reaction of a haloalkane with alcoholic KOH leads to the formation of an ________.
The reaction of a haloalkane with alcoholic KOH leads to the formation of an ________.
Match the haloalkane with the appropriate type of reaction it primarily undergoes:
Match the haloalkane with the appropriate type of reaction it primarily undergoes:
Which of the following factors does NOT affect the rate of an SN2 reaction?
Which of the following factors does NOT affect the rate of an SN2 reaction?
Haloarenes are generally more reactive than haloalkanes towards nucleophilic substitution reactions.
Haloarenes are generally more reactive than haloalkanes towards nucleophilic substitution reactions.
What is the major product formed when 2-bromobutane reacts with a strong base such as sodium ethoxide?
What is the major product formed when 2-bromobutane reacts with a strong base such as sodium ethoxide?
Name the reagent used to convert benzene to chlorobenzene.
Name the reagent used to convert benzene to chlorobenzene.
The SN1 reaction proceeds through the formation of a ________.
The SN1 reaction proceeds through the formation of a ________.
Match the reaction type with the appropriate condition or substrate characteristic:
Match the reaction type with the appropriate condition or substrate characteristic:
Which of the following haloalkanes is most likely to undergo an SN2 reaction?
Which of the following haloalkanes is most likely to undergo an SN2 reaction?
The presence of a nitro group (-NO₂) at the ortho- and para- positions increases the reactivity of haloarenes towards nucleophilic substitution.
The presence of a nitro group (-NO₂) at the ortho- and para- positions increases the reactivity of haloarenes towards nucleophilic substitution.
What is the product of the reaction between chlorobenzene and sodium hydroxide at high temperature and pressure, followed by acidification?
What is the product of the reaction between chlorobenzene and sodium hydroxide at high temperature and pressure, followed by acidification?
What type of hybridisation does the carbon atom bonded to the halogen have in haloarenes?
What type of hybridisation does the carbon atom bonded to the halogen have in haloarenes?
In an SN2 reaction, the configuration of the carbon atom undergoing substitution is ________.
In an SN2 reaction, the configuration of the carbon atom undergoing substitution is ________.
Match the method of preparation with the appropriate starting material to produce a haloalkane:
Match the method of preparation with the appropriate starting material to produce a haloalkane:
Which of the following statements best explains why haloarenes are less reactive than haloalkanes in nucleophilic substitution reactions?
Which of the following statements best explains why haloarenes are less reactive than haloalkanes in nucleophilic substitution reactions?
Elimination reactions always follow Zaitsev’s rule, regardless of the base or substrate.
Elimination reactions always follow Zaitsev’s rule, regardless of the base or substrate.
Flashcards
Haloalkanes
Haloalkanes
Compounds containing halogen atoms bonded to an sp3 hybridized carbon atom.
Haloarenes
Haloarenes
Compounds containing halogen atoms bonded to an sp2 hybridized carbon atom of an aromatic ring.
SN1 Reaction
SN1 Reaction
Reaction where a nucleophile replaces a leaving group (halogen) in a substrate.
SN2 Reaction
SN2 Reaction
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Elimination Reaction
Elimination Reaction
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Chemical Properties of Haloarenes
Chemical Properties of Haloarenes
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Study Notes
Introduction to Haloalkanes and Haloarenes
- Haloalkanes and haloarenes are organic compounds which contain halogen atoms bonded to sp3 hybridized carbon atoms in alkyl groups and sp2 hybridized carbon atoms in aryl groups, respectively.
Classification of Haloalkanes and Haloarenes
- Haloalkanes and haloarenes can be classified based on the number of halogen atoms present in the molecule as:
- Mono
- Di
- Polyhalogen compounds.
- They can also be classified based on the type of carbon atom to which the halogen is attached (primary, secondary, or tertiary).
- Allylic halides are compounds in which the halogen atom is bonded to an allylic carbon (the carbon next to a carbon-carbon double bond).
- Benzylic halides are compounds in which the halogen atom is bonded to a benzylic carbon (the carbon next to a benzene ring).
- Vinyl halides are compounds in which the halogen atom is bonded to a carbon-carbon double bond.
- Aryl halides are compounds in which the halogen atom is directly bonded to a benzene ring.
Methods of Preparation of Haloalkanes
- From Alcohols: Alcohols react with hydrogen halides (HX), phosphorus trihalides (PX3), phosphorus pentahalides (PX5), or thionyl chloride (SOCl2) to form haloalkanes.
- From Hydrocarbons:
- Alkanes can be halogenated by a free radical mechanism.
- Alkenes react with hydrogen halides (HX) to form haloalkanes, following Markovnikov's rule.
- Alkenes can also be halogenated by the addition of halogens (X2).
- Halogen exchange: Haloalkanes can be prepared by halogen exchange reactions, such as the Finkelstein reaction (reaction of alkyl chlorides/bromides with NaI in acetone) and Swarts reaction (reaction of alkyl halides with metallic fluorides like AgF, Hg2F2, CoF2, or SbF3).
Properties of Haloalkanes
- Physical Properties: Haloalkanes are generally more polar than alkanes, and their boiling points increase with increasing molecular weight and increasing polarity.
- Chemical Properties: Haloalkanes undergo nucleophilic substitution reactions (SN1 and SN2) and elimination reactions.
SN1 Reaction
- SN1 reactions are unimolecular nucleophilic substitution reactions that proceed through a two-step mechanism involving the formation of a carbocation intermediate.
- SN1 reactions are favored by polar protic solvents, tertiary alkyl halides, and weak nucleophiles.
- SN1 reactions result in racemization at the stereocenter.
SN2 Reaction
- SN2 reactions are bimolecular nucleophilic substitution reactions that occur in one step with inversion of configuration at the stereocenter.
- SN2 reactions are favored by polar aprotic solvents, primary alkyl halides, and strong nucleophiles.
Elimination Reaction
- Haloalkanes undergo elimination reactions (typically E2) in the presence of a strong base to form alkenes.
- Zaitsev's rule states that the major product of an elimination reaction is the more substituted alkene.
Methods of Preparation of Haloarenes
- Electrophilic Aromatic Substitution:
- Direct halogenation of arenes with chlorine or bromine in the presence of a Lewis acid catalyst (e.g., FeCl3, AlCl3).
- Sandmeyer's Reaction: Reaction of arenediazonium salts with CuCl/HCl, CuBr/HBr, or CuCN/KCN to form aryl chlorides, aryl bromides, or aryl cyanides, respectively.
- Gattermann Reaction involves the reaction of arenediazonium salts with copper powder and HX to yield haloarenes
Chemical Properties of Haloarenes
- Nucleophilic Aromatic Substitution: Haloarenes are less reactive than haloalkanes towards nucleophilic substitution reactions due to the resonance stabilization of the aryl halide and the difficulty of forming a carbocation intermediate.
- Reactions with Metals:
- Wurtz-Fittig reaction: Reaction of aryl halides with alkyl halides in the presence of sodium metal to form alkylbenzenes.
- Fittig reaction: Reaction of aryl halides with sodium metal to form diaryls.
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