Alcohol Homologous Series and Properties
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Questions and Answers

Which alcohol is commonly used as a high-performance fuel?

  • Ethanol
  • Butanol
  • Propanol
  • Methanol (correct)

Alcohols have lower boiling points than the corresponding alkanes with the same number of carbon atoms.

False (B)

What is the functional group present in alcohols?

hydroxyl group

In naming alcohols, the suffix __________ is added to the stem name of the longest carbon chain.

<p>ol</p> Signup and view all the answers

Match the following alcohols to their primary uses:

<p>Methanol = High-performance fuel and chemical feedstock Ethanol = Alcoholic drinks and as a fuel Butanol = Solvent and fuel Isopropanol = Disinfectant and cleaning agent</p> Signup and view all the answers

Which of the following statements best describes the volatility of alcohols compared to alkanes?

<p>Alcohols have lower volatility than alkanes. (C)</p> Signup and view all the answers

Alcohols are more polar than alkanes due to the presence of hydroxyl groups.

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

What happens to the differences in physical properties between alcohols and alkanes as the carbon chain length increases?

<p>The differences become smaller.</p> Signup and view all the answers

What is the product when a primary alcohol is heated under reflux with excess acidified potassium dichromate?

<p>Carboxylic acid (C)</p> Signup and view all the answers

Tertiary alcohols can be oxidised using acidified potassium dichromate.

<p>False (B)</p> Signup and view all the answers

What colour change occurs when dichromate (VI) ions are reduced during the oxidation of primary alcohols?

<p>Orange to green</p> Signup and view all the answers

If a primary alcohol is oxidised to an aldehyde, it must be ____ out to prevent further oxidation.

<p>distilled</p> Signup and view all the answers

Match the alcohol types with their corresponding oxidation products:

<p>Primary alcohol = Aldehyde Secondary alcohol = Ketone Tertiary alcohol = No reaction Aldehyde = Carboxylic acid</p> Signup and view all the answers

What must be done to ensure that aldehyde is formed from a primary alcohol?

<p>Gently heat and distill the aldehyde (C)</p> Signup and view all the answers

Oxidation of secondary alcohols can result in the formation of carboxylic acids.

<p>False (B)</p> Signup and view all the answers

What is the oxidising agent used in the oxidation of alcohols?

<p>Acidified potassium dichromate</p> Signup and view all the answers

Which type of alcohol is characterized by an -OH group attached to a carbon with two hydrogen atoms and one alkyl group?

<p>Primary alcohol (D)</p> Signup and view all the answers

Ethanol is classified as a secondary alcohol.

<p>False (B)</p> Signup and view all the answers

What is produced when alcohols are completely burned in the presence of oxygen?

<p>Carbon dioxide and water</p> Signup and view all the answers

The reaction of potassium dichromate (VI) with primary and secondary alcohols is used for ________.

<p>oxidation</p> Signup and view all the answers

Match the following types of alcohols with their characteristics:

<p>Primary alcohol = One alkyl group attached Secondary alcohol = Two alkyl groups attached Tertiary alcohol = Three alkyl groups attached Methanol = A simple primary alcohol</p> Signup and view all the answers

Which statement is true regarding the solubility of alcohols?

<p>Alcohols can form hydrogen bonds with water. (A)</p> Signup and view all the answers

Secondary alcohols can be oxidized by potassium dichromate (VI).

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

What changes occur in the color of potassium dichromate (VI) during the oxidation of alcohols?

<p>It changes from orange to green.</p> Signup and view all the answers

Flashcards

Dehydration

A reaction where a water molecule is removed from a molecule.

Solubility

The ability of a substance to dissolve in another substance, usually water in this context.

Hydrogen bond

A type of chemical bond where a hydrogen atom is attracted to a highly electronegative atom, like oxygen or nitrogen.

Oxidation of a primary alcohol to an aldehyde

A process where a primary alcohol is converted to an aldehyde.

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Water-insoluble compound

A compound that does not readily dissolve in water. They're non-polar and lack the ability to form hydrogen bonds with water molecules.

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Oxidation of a primary alcohol to a carboxylic acid

A process where a primary alcohol is converted to a carboxylic acid.

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Alcohol

Hydrocarbons that contain the -OH (hydroxyl) functional group, making them capable of forming hydrogen bonds.

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Oxidation of a secondary alcohol

A process where a secondary alcohol is converted to a ketone.

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Oxidation of tertiary alcohols

Tertiary alcohols do not react with oxidizing agents like acidified potassium dichromate (VI).

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Primary alcohol

An alcohol where the -OH group is attached to a carbon atom that is directly connected to two hydrogen atoms and one alkyl group.

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Secondary alcohol

An alcohol where the -OH group is attached to a carbon atom that is directly attached to one hydrogen atom and two alkyl groups.

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Dichromate (VI) reduction

Dichromate (VI) ions are reduced to chromium(III) ions in oxidation reactions.

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Oxidation of aldehydes

Aldehydes can be further oxidized to carboxylic acids.

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Tertiary alcohol

An alcohol where the -OH group is attached to a carbon atom that is directly attached to three alkyl groups (no hydrogen atoms attached).

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Oxidation of ketones

Ketones cannot be further oxidized using acidified potassium dichromate (VI).

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Combustion of alcohols

The chemical reaction of an alcohol with oxygen, producing carbon dioxide, water, and heat.

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Hydroxyl Group

A functional group containing an oxygen atom bonded to a hydrogen atom (-OH). It is responsible for the unique properties of alcohols.

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Methanol

The simplest alcohol with the formula CH3OH. Used as a high-performance fuel and a chemical feedstock.

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Ethanol

The second simplest alcohol with the formula C2H5OH. It is the main component of alcoholic drinks and is also used as a fuel and solvent.

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How are alcohols named?

The suffix '-ol' is added to the stem name of the longest carbon chain in an alcohol molecule.

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Why are alcohols less volatile?

Alcohols have higher melting points and lower volatility compared to alkanes with the same number of carbon atoms due to the presence of strong hydrogen bonding between alcohol molecules.

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Intermolecular Forces

The intermolecular forces responsible for holding molecules together in liquids and solids.

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Study Notes

The Alcohol Homologous Series

  • Alcohols contain a hydroxyl (-OH) functional group.
  • The hydroxyl group affects both the physical and chemical properties of alcohols.
  • Methanol (CH3OH) is the simplest alcohol.
  • Methanol is a high-performance fuel due to efficient combustion.
  • Methanol is also a crucial chemical feedstock in various industrial processes.
  • Methanol can be converted into polymers, paints, solvents, and more.
  • Ethanol (C2H5OH) is the second alcohol in the homologous series.
  • Ethanol is primarily used in alcoholic beverages and as a fuel.
  • Ethanol is also used as a solvent and feedstock.

Naming Alcohols

  • The suffix "-ol" is added to the stem name of the longest carbon chain.
  • The position of the alcohol functional group in the chain is indicated with a number.

Physical Properties

  • Alcohols are less volatile than alkanes with the same number of carbon atoms.
  • Alcohols have higher melting points than corresponding alkanes.
  • Alcohols exhibit greater water solubility compared to alkanes.
  • The differences in properties lessen with increasing carbon chain length.
  • Alkanes have nonpolar bonds due to similar electronegativity of hydrogen and carbon.
  • Alkanes have weak London dispersion forces.
  • Alcohols have a polar O-H bond due to electronegativity difference between oxygen and hydrogen.
  • Alcohols are polar molecules with weak London dispersion forces and stronger hydrogen bonds.
  • Hydrogen bonds between polar O-H groups in alcohols lead to higher boiling points compared to alkanes.
  • Alcohols can form hydrogen bonds with water molecules, causing high water solubility.

Classifying Alcohols

  • Alcohols are categorized as primary, secondary, or tertiary based on the number of alkyl groups attached to the carbon atom bearing the hydroxyl group.

  • Primary alcohols have one alkyl group.

  • Secondary alcohols have two alkyl groups.

  • Tertiary alcohols have three alkyl groups.

  • Methanol and ethanol are primary alcohols.

Combustion of Alcohols

  • Alcohols burn completely in excess oxygen to produce carbon dioxide and water.
  • The heat released increases with increasing carbon chain length.
  • The equation for the complete combustion of ethanol is C2H5OH(l) + 3O2(g) → 2CO2(g) + 3H2O(l)

Oxidation of Alcohols

  • Primary alcohols can be oxidized to aldehydes or carboxylic acids, depending on reaction conditions.
  • Secondary alcohols are oxidized to ketones.
  • Tertiary alcohols do not undergo oxidation.
  • Oxidizing agents like potassium dichromate (VI) can be used to determine if an alcohol is oxidized.
  • Orange dichromate (VI) reduces to a green chromium (III) solution during the oxidation.

Dehydration of Alcohols

  • Dehydration is the reaction that removes a water molecule from the starting alcohol.
  • The process is an elimination reaction, creating an alkene as the product.
  • Concentrated sulfuric or phosphoric acid are used as catalysts in this process.

Preparation of Haloalkanes

  • Alcohols can react with hydrogen halides (like HBr) to produce haloalkanes.
  • This reaction usually involves heating the alcohol with a hydrogen halide in the presence of a catalyst like sulfuric acid.

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Description

This quiz covers the fundamentals of the alcohol homologous series, including the properties and naming conventions of alcohols. It highlights methanol and ethanol, their uses, and how the hydroxyl group influences their characteristics. Test your understanding of alcohols and their significance in chemical applications.

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