Alcohols and Oxidation Reactions Quiz
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Questions and Answers

What is the primary use of methanol?

  • As a vitamin supplement
  • As a food preservative
  • As a main ingredient in alcoholic drinks
  • As a fuel (correct)

Ethanol is primarily used as a high-performance fuel.

False (B)

What group is responsible for the properties of alcohols?

hydroxyl group

The suffix _____ is added to the stem name of alcohols.

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

Match the following alcohols with their primary usage:

<p>Methanol = High-performance fuel Ethanol = Alcoholic drinks and fuel</p> Signup and view all the answers

What is the main purpose of using an excess of acidified potassium dichromate(VI) when oxidizing a primary alcohol?

<p>To ensure all of the alcohol is oxidized (D)</p> Signup and view all the answers

Heating under reflux allows any aldehyde formed to remain unchanged in the reaction.

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

What type of alcohol is required to produce a carboxylic acid through oxidation with acidified potassium dichromate(VI)?

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

When a primary alcohol is oxidized, the reaction results in the formation of a ______.

<p>carboxylic acid</p> Signup and view all the answers

Match the following components of the oxidation reaction with their roles:

<p>Primary alcohol = Substrate being oxidized Acidified potassium dichromate(VI) = Oxidizing agent Reflux = Process to ensure complete reaction Carboxylic acid = Final product of the reaction</p> Signup and view all the answers

What is produced when alcohol burns completely in a plentiful supply of oxygen?

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

The oxidation of primary alcohols always results in the production of carboxylic acids, regardless of the conditions.

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

What color change occurs when dichromate (VI) ions are reduced to chromium(III) ions?

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

The complete combustion of ethanol is represented by the equation $C_2H_5OH(l) + 3O_2(g) ightarrow 2CO_2(g) + 3H_2O(l)$, where ethanol is a type of ______.

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

Match the following alcohols with their corresponding oxidized products:

<p>Butan-1-ol = Butanal Primary alcohol = Aldehyde or Carboxylic acid Secondary alcohol = Ketone Tertiary alcohol = No reaction</p> Signup and view all the answers

Which of the following is a characteristic feature of tertiary alcohols?

<p>The -OH group is attached to a carbon with no hydrogen atoms and three alkyl groups. (A)</p> Signup and view all the answers

2-Methylpropan-2-ol is an example of a tertiary alcohol.

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

Name one example of a tertiary alcohol.

<p>2-Methylbutan-2-ol</p> Signup and view all the answers

In tertiary alcohols, the carbon atom to which the -OH group is attached has __________ alkyl groups.

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

Match the following tertiary alcohols with their structures:

<p>2-Methylpropan-2-ol = A branched structure with the -OH on the central carbon with three tertiary branches. 2-Methylbutan-2-ol = A branched structure with the -OH on the second carbon of a four-carbon chain.</p> Signup and view all the answers

Which of the following is an example of a secondary alcohol?

<p>Propan-2-ol (B)</p> Signup and view all the answers

A secondary alcohol has the -OH group attached to a carbon atom that is connected to two hydrogen atoms.

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

Name a secondary alcohol that has four carbon atoms.

<p>Pentan-3-ol</p> Signup and view all the answers

In a secondary alcohol, the -OH group is attached to a carbon that is connected to one hydrogen atom and ____ alkyl groups.

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

Match the following secondary alcohols with their carbon chain lengths:

<p>Propan-2-ol = 3 carbon atoms Pentan-3-ol = 5 carbon atoms</p> Signup and view all the answers

What color does the acidified dichromate(VI) turn when added to a tertiary alcohol?

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

Tertiary alcohols can undergo oxidation reactions.

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

What happens to the color of dichromate(VI) when it reacts with a tertiary alcohol?

<p>The color remains orange.</p> Signup and view all the answers

Tertiary alcohols are resistant to __________ reactions.

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

Match the following types of alcohols with their oxidation behavior:

<p>Tertiary alcohols = Do not undergo oxidation Primary alcohols = Oxidize to aldehydes Secondary alcohols = Oxidize to ketones Saturated alcohols = Behavior depends on structure</p> Signup and view all the answers

What characterizes a primary alcohol?

<p>The -OH group is attached to a carbon with two hydrogens and one alkyl group. (C)</p> Signup and view all the answers

Methanol and ethanol are classified as secondary alcohols.

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

What is the classification of methanol in the alcohol homologous series?

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

A primary alcohol has a -OH group attached to a carbon with two _________ and one alkyl group.

<p>hydrogen atoms</p> Signup and view all the answers

Match the following alcohols with their classification:

<p>Methanol = Primary Ethanol = Primary Isopropanol = Secondary Tert-butanol = Tertiary</p> Signup and view all the answers

What is the main product formed when an alcohol undergoes dehydration?

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

What is the product formed when a secondary alcohol is oxidized?

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

It is possible to further oxidize ketones using acidified dichromate(VI) ions.

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

Dehydration of alcohol involves the addition of a water molecule to the reaction.

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

What method is used to prepare an aldehyde from a primary alcohol?

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

What type of reaction is dehydration of alcohol categorized as?

<p>Elimination reaction</p> Signup and view all the answers

During dehydration of alcohols, _____ is often used as an acid catalyst.

<p>concentrated sulfuric acid</p> Signup and view all the answers

To prepare a carboxylic acid from a primary alcohol, one must heat the alcohol under ______.

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

Match the following components involved in dehydration reactions with their roles:

<p>Alcohol = Starting material for dehydration Acid catalyst = Facilitates the reaction Alkene = Product of dehydration Water = Byproduct of the reaction</p> Signup and view all the answers

What is produced when an alcohol reacts with hydrogen halides?

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

Sulfuric acid is not needed during the reaction of alcohols with hydrogen halides.

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

What is the role of sodium bromide in the preparation of haloalkanes?

<p>It reacts with sulfuric acid to produce hydrogen bromide.</p> Signup and view all the answers

The process used to heat alcohols with hydrogen halides is called __________.

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

Match the following components with their roles in the reaction of alcohols with hydrogen halides:

<p>NaBr = Source of bromide ion Hâ‚‚SOâ‚„ = Catalyst that generates HBr HBr = Reagent that converts alcohol to haloalkane Alcohol = Starting material for haloalkane synthesis</p> Signup and view all the answers

Flashcards

Oxidation of Primary Alcohol to Carboxylic Acid

A reaction where a primary alcohol is converted to a carboxylic acid using acidified potassium dichromate(VI).

Reflux

Reflux is a technique used in chemistry where the reaction mixture is heated to boiling point and the vapors are condensed back into the reaction vessel.

Excess Oxidizing Agent

An excess of acidified potassium dichromate(VI) ensures that all of the alcohol is oxidized to the carboxylic acid.

Heating Under Reflux

Heating under reflux ensures that any aldehyde formed initially in the reaction also undergoes oxidation to the carboxylic acid.

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Carboxylic Acid

A chemical compound containing a carbonyl group (-C=O) bonded to a hydroxyl group (-OH).

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Alcohol Homologous Series

A group of organic compounds with the same general formula, but with each successive member differing by a CH2 unit. In alcohols, members of the homologous series differ by a CH2 unit and contain the -OH functional group.

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Hydroxyl Group

The functional group present in alcohols, consisting of a hydrogen atom bonded to an oxygen atom.

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Methanol

The simplest member of the alcohol homologous series, with the formula CH3OH. It is used as a high-performance fuel and a chemical feedstock.

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Ethanol

The second member of the alcohol homologous series, with the formula C2H5OH. It is primarily used in alcoholic drinks and as a fuel.

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The -ol Suffix

The suffix added to the stem name of the longest carbon chain when naming alcohols. The position of the hydroxyl group is indicated using a number.

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Combustion of Alcohols

The process of burning a substance in the presence of oxygen, releasing heat and producing carbon dioxide and water.

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Oxidation of Alcohols

The process of adding oxygen to a molecule, often involving the use of an oxidizing agent.

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Primary Alcohols

Alcohols containing a hydroxyl group (-OH) attached to a carbon atom that is bonded to only one other carbon atom.

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Aldehyde

The product formed when a primary alcohol is oxidized under controlled conditions. Aldehydes contain a carbonyl group (-C=O) at the end of the carbon chain.

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What is a primary alcohol?

A primary alcohol has its -OH group attached to a carbon atom that is bonded to two hydrogen atoms and one alkyl group. Methanol is an exception, having three hydrogen atoms and no alkyl groups.

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What is a secondary alcohol?

A secondary alcohol has its -OH group attached to a carbon atom that is bonded to one hydrogen atom and two alkyl groups.

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What is a tertiary alcohol?

A tertiary alcohol has its -OH group attached to a carbon atom that is bonded to three alkyl groups.

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Give two examples of tertiary alcohols.

2-Methylpropan-2-ol and 2-Methylbutan-2-ol are both examples of common tertiary alcohols.

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What is unusual about the carbon atom in a tertiary alcohol?

The carbon atom that the -OH group is attached to in a tertiary alcohol is not directly bonded to any hydrogen atoms.

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What is the surrounding environment of the carbon in a tertiary alcohol?

The carbon atom with the -OH group is bonded to three carbon atoms, each part of an alkyl group, in a tertiary alcohol.

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Describe the structure of a tertiary alcohol.

The -OH group in a tertiary alcohol is directly attached to a carbon which is connected to three alkyl groups, with no hydrogen atoms attached.

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Oxidation of Tertiary Alcohols

Tertiary alcohols cannot be oxidized by oxidizing agents like acidified potassium dichromate(VI).

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Tertiary Alcohol Structure

The carbon atom attached to the hydroxyl group in a tertiary alcohol is bonded to three other carbon atoms.

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Acidified Dichromate(VI)

Acidified dichromate(VI) is an oxidizing agent that changes color from orange to green when it oxidizes an alcohol.

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Why Tertiary Alcohols Don't Oxidize

The inability of tertiary alcohols to be oxidized is due to the lack of a hydrogen atom on the carbon attached to the hydroxyl group, which is a requirement for oxidation.

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Oxidation Reaction

Oxidation reactions involve the loss of electrons and the gain of oxygen atoms, leading to the formation of a new compound.

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Why is propan-2-ol a secondary alcohol?

In propan-2-ol, the -OH group is attached to the second carbon atom, which is bonded to two methyl groups and one hydrogen atom. This makes it a secondary alcohol.

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Why is pentan-3-ol a secondary alcohol?

In pentan-3-ol, the -OH group is attached to the third carbon atom, which is bonded to an ethyl group, a methyl group, and one hydrogen atom. This makes it a secondary alcohol.

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How do you identify the position of the -OH group in alcohol names?

The number in the name of the alcohol (e.g., propan-2-ol) indicates the carbon to which the -OH group is attached.

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How do secondary alcohols differ from primary and tertiary alcohols?

Secondary alcohols differ from primary alcohols, which have the -OH group attached to a carbon that is bonded to one alkyl group and two hydrogen atoms (or one alkyl group and a hydrogen atom and a different functional group), and tertiary alcohols, where the -OH group is attached to a carbon bonded to three alkyl groups.

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Oxidation of Primary Alcohol to Aldehyde

A primary alcohol can be oxidized to an aldehyde by using distillation to remove the aldehyde as it forms, preventing further oxidation.

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Oxidation of Secondary Alcohol

Secondary alcohols are oxidized to ketones when reacted with an oxidizing agent like acidified dichromate(VI) ions.

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Further Oxidation of Ketones

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

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Complete Oxidation of Secondary Alcohol

To ensure complete oxidation of a secondary alcohol to a ketone, the reaction is heated under reflux. The color change of the dichromate(VI) ions from orange to green indicates completion.

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Dehydration Reaction

A chemical reaction that involves the removal of a water molecule from a starting material, typically in the presence of an acid catalyst.

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Elimination Reaction

A type of chemical reaction where a molecule loses atoms to form a smaller molecule, specifically, a water molecule is eliminated from an alcohol to form an alkene.

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Alkene

A chemical compound that contains a carbon-carbon double bond. They are unsaturated hydrocarbons and are often found in fuels and polymers.

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Dehydration of Alcohol

A reaction in which an alcohol is heated in the presence of a strong acid catalyst to form an alkene and water.

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Acid Catalyst

A substance that speeds up a chemical reaction without being consumed in the process. In the case of alcohol dehydration, strong acids like sulfuric acid (H₂SO₄) or phosphoric acid (H₃PO₄) are used.

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Reaction of Alcohols with Hydrogen Halides

A reaction where alcohols are transformed into haloalkanes using hydrogen halides (like HBr).

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In situ Formation

The process of producing a substance (like HBr) within the reaction mixture itself, rather than adding it pre-made.

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Haloalkane

A chemical compound that contains a carbon atom bonded to a halogen atom. They are used as solvents, refrigerants and in pharmaceuticals.

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Role of Sulfuric Acid and Sodium Halide

Sulfuric acid (Hâ‚‚SOâ‚„) is used to react with a sodium halide (like NaBr) to generate hydrogen bromide (HBr) which then reacts with the alcohol.

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Study Notes

Preparation of carboxylic acids

  • If a primary alcohol is heated strongly under reflux, with an excess of acidified potassium dichromate(VI), a carboxylic acid is formed
  • Use of an excess of the acidified potassium dichromate(VI) ensures that all of the alcohol is oxidised
  • Heating under reflux ensures that any aldehyde formed initially in the reaction also undergoes oxidation to the carboxylic acid

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Description

Test your knowledge on the properties, uses, and oxidation reactions of alcohols. This quiz covers topics such as the primary uses of methanol, the role of acidified potassium dichromate(VI), and the types of alcohols involved in these reactions. Challenge yourself and see how well you understand alcohol chemistry!

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