Haloalkanes and Haloarenes Overview
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Questions and Answers

What type of halide is dichloromethane classified as?

  • Dihalide (correct)
  • Polyhalide
  • Aryl halide
  • Monohalide

What is the main reason why the preparation of aryl halides is challenging?

  • Aryl halides can only be prepared through indirect methods.
  • Aryl halides are always unstable and decompose.
  • The carbon-oxygen bond in phenols has a partial double bond character. (correct)
  • The carbon-oxygen bond in phenols is less stable than a single bond.

Which of the following compounds is considered an aryl halide?

  • Iodoform
  • Carbon tetrachloride
  • Chloroform
  • Bromobenzene (correct)

Which of the following methods can yield vic-dibromides during alkene reactions?

<p>Addition of bromine in CCl4 solution. (D)</p> Signup and view all the answers

What is the key characteristic of the products obtained from the free radical chlorination of alkanes?

<p>They result in a complex mixture of isomeric products. (B)</p> Signup and view all the answers

What is the result of nucleophilic substitution in SN2 reactions of chiral alkyl halides?

<p>Inversion of configuration (A)</p> Signup and view all the answers

According to Markovnikov's rule, which product predominates when propene reacts with hydrogen halides?

<p>The more substituted alkyl halide. (C)</p> Signup and view all the answers

How are alkyl halides generally prepared?

<p>By free radical halogenation of alkanes (A)</p> Signup and view all the answers

Which of the following statements about DDT is true?

<p>It accumulates in fatty tissues. (C)</p> Signup and view all the answers

What kind of reaction is the Finkelstein reaction?

<p>Substitution of alkyl halides with sodium iodide. (A)</p> Signup and view all the answers

Which type of halide is characterized by a halogen bonded to an sp2-hybridised carbon in a carbon-carbon double bond?

<p>Vinylic halide (C)</p> Signup and view all the answers

How are geminal halides specifically defined?

<p>Halogen atoms on the same carbon atom (A)</p> Signup and view all the answers

How many different monochloro structural isomers can be formed from the free radical monochlorination of (CH3)2CHCH2CH3?

<p>Four. (A)</p> Signup and view all the answers

What classification best describes a compound containing three halogen atoms?

<p>Trihalide (A)</p> Signup and view all the answers

What occurs during the addition of bromine to an alkene in a laboratory setting?

<p>Discharge of reddish brown color. (B)</p> Signup and view all the answers

What is the IUPAC naming convention for dihalogen derivatives of benzene?

<p>Using the numerals 1,2; 1,3; and 1,4 (A)</p> Signup and view all the answers

What is a characteristic feature of the boiling points of organohalogen compounds compared to corresponding hydrocarbons?

<p>Higher boiling points due to dipole-dipole interactions (C)</p> Signup and view all the answers

Why is the separation of products from free radical halogenation of alkanes difficult?

<p>The reaction leads to a complex mixture of isomeric compounds. (D)</p> Signup and view all the answers

Which of the following describes an aryl halide?

<p>Halogen directly bonded to an aromatic ring (D)</p> Signup and view all the answers

In nucleophilic substitution reactions, what role does the polarity of the carbon-halogen bond play?

<p>It influences the reaction mechanism employed. (C)</p> Signup and view all the answers

Which of the following best describes vicinal halides?

<p>Halogens on adjacent carbon atoms (A)</p> Signup and view all the answers

In the nomenclature of alkyl halides, how are they commonly named?

<p>By naming the alkyl group followed by the halide (D)</p> Signup and view all the answers

What is a characteristic feature of benzylic halides?

<p>Halogen bonded to an sp3-hybridised carbon attached to an aromatic ring (A)</p> Signup and view all the answers

What type of halides do the terms alkylidene or alkylene dihalides refer to?

<p>Dihalogen compounds with the same halogen atoms (C)</p> Signup and view all the answers

Flashcards

Benzylic halide

A compound where a halogen atom is bonded to a carbon atom attached to an aromatic ring.

Vinylic halide

A compound where a halogen atom is bonded to a carbon atom in a carbon-carbon double bond.

Allylic halide

A compound where a halogen atom is bonded to a carbon atom next to a carbon-carbon double bond.

Aryl halide

A compound where a halogen atom is directly bonded to a carbon atom in an aromatic ring.

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Geminal dihalide

A dihalide where both halogen atoms are on the same carbon atom.

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Vicinal dihalide

A dihalide where halogen atoms are on adjacent carbon atoms.

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Free radical halogenation of alkanes

A reaction where a halogen atom replaces a hydrogen atom in an alkane, creating a mixture of products.

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Mono- and polyhaloalkanes

Compounds formed when one or more halogen atoms substitute hydrogen atoms in an alkane.

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Alkene addition reactions

Reactions where halogens or hydrogen halides add across a carbon-carbon double bond.

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Markovnikov's rule

In alkene addition reactions, the hydrogen atom adds to the carbon with more hydrogens already.

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Finkelstein reaction

A reaction used to prepare alkyl iodides from alkyl chlorides or bromides using NaI and dry acetone.

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Partial double bond character

Phenols have a strong carbon-oxygen bond, which behaves more like a double bond than a single bond.

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Aryl halides

Aromatic compounds where a halogen is directly bonded to an aromatic ring.

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Vic-dibromide

A compound with two bromine atoms on adjacent carbon atoms.

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Structural isomers

Molecules with the same molecular formula but different arrangements of atoms.

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DDT Resistance

Some insects developed resistance to the pesticide DDT.

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DDT Toxicity

DDT is harmful to fish.

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DDT Chemical Stability

DDT stays in the environment for a long time.

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DDT Fat Solubility

DDT dissolves in fats and oils.

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DDT Metabolism

Animals don't break down DDT quickly.

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DDT Ban (US)

The United States stopped using DDT in 1973.

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Alkyl/Aryl Halides

Organic compounds with one or more halogen atoms.

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Carbon-Halogen Bond Polarity

Halogen is more electronegative than carbon, creating a partial positive on carbon.

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Alkyl Halide Preparation

Made by reacting alkanes with halogens, alkenes with halogen acids, or by reacting alcohols with agents like phosphorus halides or thionyl chloride.

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Aryl Halide Preparation

Prepared by electrophilic substitution on aromatic rings.

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Halogen Exchange Method

A method for making fluorides and iodides.

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Boiling Points of Organohalogen Compounds

Higher than corresponding hydrocarbons due to stronger intermolecular forces.

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Solubility of Organohalogen Compounds

Slightly soluble in water, completely soluble in organic solvents.

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Nucleophilic Substitution Reactions

Reactions where a nucleophile replaces a halogen atom.

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SN1 and SN2 Reactions

Different types of nucleophilic substitution reactions based on their kinetics.

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Chirality in SN Reactions

Chirality affects the reaction pathway and product configuration.

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Study Notes

Haloalkanes and Haloarenes

  • Halogenated compounds persist in the environment due to resistance to breakdown by soil bacteria.
  • Replacement of hydrogen atoms in an aliphatic or aromatic hydrocarbon by halogen atoms forms alkyl halides (haloalkanes) and aryl halides (haloarenes).
  • Haloalkanes have halogen atoms attached to sp³ hybridized carbon atoms in an alkyl group.
  • Haloarenes have halogen atoms attached to sp² hybridized carbon atoms in an aryl group.
  • Many halogen-containing organic compounds occur in nature and are clinically useful.
  • These compounds are used as solvents and starting materials for various organic compounds.
  • Examples include Chloramphenicol (antibiotic) and Thyroxine (hormone).
  • Also used as anesthetics (e.g., halothane) and potential blood substitutes.

Classification

  • Classified as mono, di, or polyhalogen compounds based on the number of halogen atoms.
  • Alkyl halides (or haloalkanes) are further classified as primary, secondary, or tertiary based on the nature of the carbon atom to which the halogen atom is attached.
  • Allylic halides have halogen attached to an sp³-hybridized carbon adjacent to a double bond.
  • Benzylic halides have halogen attached to an sp³-hybridized carbon adjacent to an aromatic ring.

Nomenclature

  • Common names for alkyl halides are based on the alkyl group followed by the halide name.
  • IUPAC naming follows the prefix halo for the type of halogen, followed by the parent hydrocarbon name.
  • Specific prefixes (e.g., o-, m-, p-) are used for dihalogenated benzene derivatives in common system, but in IUPAC system, numerical prefixes (1,2; 1,3; 1,4) are used.

Methods of Preparation

  • Hydroxyl groups in alcohols are replaced by halogen using concentrated halogen acids, phosphorus halides, or thionyl chloride.
  • Tertiary alcohols react with concentrated HCl at room temperature to yield alkyl halides.
  • Primary and secondary alcohols react with HCl in the presence of ZnClâ‚‚.
  • Alcohols are treated with sodium/potassium iodide in 95% orthophosphoric acid for the synthesis of alkyl iodides.
  • Alkyl chlorides are prepared by the reaction of alcohols with dry hydrogen chloride gas or a mixture of the alcohol and concentrated aqueous halogen acid.
  • Alkyl halides are also prepared by free radical halogenation or addition of hydrogen halides to alkenes.
  • Aryl halides are prepared by electrophilic substitution of arenes with Clâ‚‚/Brâ‚‚ in presence of Lewis acid catalysts( Fe/ FeCl₃ )
  • Amines can be converted into aryl halides by Sandmeyer's reaction.

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Haloalkanes and Haloarenes PDF

Description

Explore the properties and classifications of halogenated compounds, including haloalkanes and haloarenes. Learn about their environmental persistence, clinical uses, and various organic applications. This quiz covers the nature of the compounds and their significance in chemistry.

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