An alcohol is an organic compound containing a hydroxyl functional group (-OH). The general formula is C n H 2n+1 OH and alcohols are named using the suffix -ol.

What is the general formula for alcohols?

The general formula for alcohols is C n H 2n+1 OH. For example, methanol is CH 3 OH (n = 1) and ethanol is C 2 H 5 OH (n = 2).

A diol is an alcohol that contains two hydroxyl (-OH) groups within the same molecule.

True or False? Ethanol (CH 3 CH 2 OH) is classified as a primary alcohol.

True. In ethanol, the carbon atom bonded to the -OH group is attached to only one other carbon atom (the CH 3 group), which is the definition of a primary alcohol .

Define primary alcohol

A primary alcohol is one in which the carbon atom bonded to the -OH group is attached to only one other carbon atom (or alkyl group). For example, ethanol (CH 3 CH 2 OH) is a primary alcohol.

Define secondary alcohol

A secondary alcohol is one in which the carbon atom bonded to the -OH group is attached to two other carbon atoms (or alkyl groups). For example, propan-2-ol is a secondary alcohol.

Alcohols are named by taking the parent .......... name and replacing the final e with the suffix ......... .

Alcohols are named by taking the parent alkane name and replacing the final e with the suffix -ol .

Define tertiary alcohol

A tertiary alcohol is one in which the carbon atom bonded to the -OH group is attached to three other carbon atoms (or alkyl groups).

What are the products of the complete combustion of an alcohol?

Complete combustion of an alcohol produces carbon dioxide and water . For example: C 2 H 5 OH + 3O 2 → 2CO 2 + 3H 2 O

What are the organic and inorganic products when an alcohol reacts with PCl 5 ?

The organic product is a chloroalkane . The inorganic products are phosphoryl chloride (POCl 3 ) and hydrogen chloride (HCl gas). For example: CH 3 CH 2 CH 2 OH + PCl 5 → CH 3 CH 2 CH 2 Cl + POCl 3 + HCl.

The dehydration of ethanol using concentrated phosphoric acid produces .......... and .......... as products.

The dehydration of ethanol using concentrated phosphoric acid produces ethene and water as products.

How can PCl 5 be used as a qualitative test for the presence of an -OH group?

PCl 5 is added to the unknown liquid at room temperature. The evolution of steamy fumes (HCl gas) confirms the presence of a hydroxyl (-OH) group .

What are the conditions and reagents for converting an alcohol to a bromoalkane?

The alcohol is warmed with a mixture of potassium bromide (KBr) and 50% concentrated sulfuric acid . The KBr and H 2 SO 4 first react to produce HBr, which then reacts with the alcohol to form the bromoalkane and water.

True or False? Shaking with concentrated hydrochloric acid at room temperature is a suitable method to chlorinate both primary and tertiary alcohols.

False. This method only works for tertiary alcohols . Primary and secondary alcohols do not react with HCl under these conditions. PCl 5 is required instead.

What are the conditions and reagents for converting an alcohol to an iodoalkane?

The alcohol is heated under reflux with a mixture of red phosphorus and iodine (I 2 ). The red phosphorus and iodine react first to form PI 3 , which then reacts with the alcohol to produce the iodoalkane and H 3 PO 3 .

What reagent is used to dehydrate an alcohol to form an alkene?

Concentrated phosphoric acid (H 3 PO 4 ) is used as the dehydrating agent. The alcohol is heated with concentrated phosphoric acid, removing the -OH group and a hydrogen from an adjacent carbon to form a C=C double bond.

Why is 50% sulfuric acid (not concentrated) used in the bromination of alcohols?

Concentrated sulfuric acid would oxidise the bromide ions (Br - ) to bromine (Br 2 ), giving different and unwanted products. Using 50% sulfuric acid prevents this oxidation while still generating sufficient HBr to react with the alcohol.

What are the oxidation products of primary , secondary and tertiary alcohols?

Primary alcohols are oxidised first to aldehydes and then further to carboxylic acids . Secondary alcohols are oxidised to ketones only. Tertiary alcohols are not oxidised .

Define Fehling's solution

Fehling's solution is an alkaline solution containing copper(II) ions that acts as an oxidising agent. When warmed with an aldehyde, the clear blue solution turns opaque due to the formation of a red precipitate of copper(I) oxide. Ketones give a negative result.

What colour change is observed when acidified potassium dichromate(VI) is used to oxidise an alcohol?

The solution changes from orange to green . The orange Cr 2 O 7 2- ions are reduced to green Cr 3+ ions as they oxidise the alcohol.

Define Tollens' reagent

Tollens' reagent is an aqueous alkaline solution of silver nitrate in excess ammonia (ammoniacal silver nitrate). When warmed with an aldehyde, Ag + ions are reduced to silver atoms, forming a silver mirror on the inside of the test tube. Ketones give a negative result.

In distillation with addition, the aldehyde distils off immediately because it has a much .......... boiling point than the .......... reactant.

In distillation with addition, the aldehyde distils off immediately because it has a much lower boiling point than the alcohol reactant.

How do you obtain an aldehyde (not a carboxylic acid) from the oxidation of a primary alcohol?

Use distillation with addition : the oxidising agent (acidified K 2 Cr 2 O 7 ) is heated while the alcohol is slowly added. The aldehyde distils off as soon as it forms due to its lower boiling point, preventing further oxidation to a carboxylic acid.

How do you obtain a carboxylic acid from the full oxidation of a primary alcohol?

Heat the alcohol under reflux with excess acidified K 2 Cr 2 O 7 . Refluxing keeps all products in the reaction mixture, allowing the aldehyde intermediate to be further oxidised to a carboxylic acid.

True or False? Fehling's solution gives a positive result (red precipitate) when warmed with a ketone.

False. Ketones cannot be oxidised , so they give a negative result with Fehling's solution. Only aldehydes produce the red copper(I) oxide precipitate.

True or False? Heating a secondary alcohol under reflux with excess acidified K 2 Cr 2 O 7 produces a ketone.

True. Secondary alcohols are oxidised to ketones . Unlike aldehydes, ketones cannot be further oxidised, so refluxing does not produce a different product.

Why must acidified potassium dichromate(VI) be used to oxidise alcohols rather than the dichromate solution alone?

The reduction of dichromate ions requires H + ions to proceed. The acid (such as dilute sulfuric acid) provides these H + ions, allowing Cr 2 O 7 2- to act as an effective oxidising agent.

International A Level (IAL)ChemistryEdexcelFlashcards2. Energetics, Group Chemistry, Halogenoalkanes & AlcoholsOrganic Chemistry: Alcohols

Organic Chemistry: Alcohols (Edexcel International A Level (IAL) Chemistry): Flashcards

Exam code: YCH11

1/27

0Still learning

Know0

FrontAlcohols - Introduction
Define alcohol

Was this flashcard helpful?

Cards in this collection (27)

Define alcohol
An alcohol is an organic compound containing a hydroxyl functional group (-OH).
The general formula is C_nH_2n+1OH and alcohols are named using the suffix -ol.
What is the general formula for alcohols?
The general formula for alcohols is C_nH_2n+1OH.
For example, methanol is CH₃OH (n = 1) and ethanol is C₂H₅OH (n = 2).
Define diol
A diol is an alcohol that contains two hydroxyl (-OH) groups within the same molecule.
True or False?
Ethanol (CH₃CH₂OH) is classified as a primary alcohol.
True.
In ethanol, the carbon atom bonded to the -OH group is attached to only one other carbon atom (the CH₃ group), which is the definition of a primary alcohol.
Define primary alcohol
A primary alcohol is one in which the carbon atom bonded to the -OH group is attached to only one other carbon atom (or alkyl group).
For example, ethanol (CH₃CH₂OH) is a primary alcohol.
Define secondary alcohol
A secondary alcohol is one in which the carbon atom bonded to the -OH group is attached to two other carbon atoms (or alkyl groups).
For example, propan-2-ol is a secondary alcohol.
Alcohols are named by taking the parent .......... name and replacing the final e with the suffix ......... .
Alcohols are named by taking the parent alkane name and replacing the final e with the suffix -ol.
Define tertiary alcohol
A tertiary alcohol is one in which the carbon atom bonded to the -OH group is attached to three other carbon atoms (or alkyl groups).
What are the products of the complete combustion of an alcohol?
Complete combustion of an alcohol produces carbon dioxide and water.
For example: C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O
What are the organic and inorganic products when an alcohol reacts with PCl₅?
The organic product is a chloroalkane.
The inorganic products are phosphoryl chloride (POCl₃) and hydrogen chloride (HCl gas). For example: CH₃CH₂CH₂OH + PCl₅ → CH₃CH₂CH₂Cl + POCl₃ + HCl.
The dehydration of ethanol using concentrated phosphoric acid produces .......... and .......... as products.
The dehydration of ethanol using concentrated phosphoric acid produces ethene and water as products.
How can PCl₅ be used as a qualitative test for the presence of an -OH group?
PCl₅ is added to the unknown liquid at room temperature.
The evolution of steamy fumes (HCl gas) confirms the presence of a hydroxyl (-OH) group.
What are the conditions and reagents for converting an alcohol to a bromoalkane?
The alcohol is warmed with a mixture of potassium bromide (KBr) and 50% concentrated sulfuric acid.
The KBr and H₂SO₄ first react to produce HBr, which then reacts with the alcohol to form the bromoalkane and water.
True or False?
Shaking with concentrated hydrochloric acid at room temperature is a suitable method to chlorinate both primary and tertiary alcohols.
False.
This method only works for tertiary alcohols. Primary and secondary alcohols do not react with HCl under these conditions. PCl₅ is required instead.
What are the conditions and reagents for converting an alcohol to an iodoalkane?
The alcohol is heated under reflux with a mixture of red phosphorus and iodine (I₂).
The red phosphorus and iodine react first to form PI₃, which then reacts with the alcohol to produce the iodoalkane and H₃PO₃.
What reagent is used to dehydrate an alcohol to form an alkene?
Concentrated phosphoric acid (H₃PO₄) is used as the dehydrating agent.
The alcohol is heated with concentrated phosphoric acid, removing the -OH group and a hydrogen from an adjacent carbon to form a C=C double bond.
Why is 50% sulfuric acid (not concentrated) used in the bromination of alcohols?
Concentrated sulfuric acid would oxidise the bromide ions (Br^-) to bromine (Br₂), giving different and unwanted products.
Using 50% sulfuric acid prevents this oxidation while still generating sufficient HBr to react with the alcohol.
What are the oxidation products of primary, secondary and tertiary alcohols?
Primary alcohols are oxidised first to aldehydes and then further to carboxylic acids.
Secondary alcohols are oxidised to ketones only. Tertiary alcohols are not oxidised.
Define Fehling's solution
Fehling's solution is an alkaline solution containing copper(II) ions that acts as an oxidising agent.
When warmed with an aldehyde, the clear blue solution turns opaque due to the formation of a red precipitate of copper(I) oxide. Ketones give a negative result.
What colour change is observed when acidified potassium dichromate(VI) is used to oxidise an alcohol?
The solution changes from orange to green.
The orange Cr₂O₇^2- ions are reduced to green Cr³⁺ ions as they oxidise the alcohol.
Define Tollens' reagent
Tollens' reagent is an aqueous alkaline solution of silver nitrate in excess ammonia (ammoniacal silver nitrate).
When warmed with an aldehyde, Ag⁺ ions are reduced to silver atoms, forming a silver mirror on the inside of the test tube. Ketones give a negative result.
In distillation with addition, the aldehyde distils off immediately because it has a much .......... boiling point than the .......... reactant.
In distillation with addition, the aldehyde distils off immediately because it has a much lower boiling point than the alcohol reactant.
How do you obtain an aldehyde (not a carboxylic acid) from the oxidation of a primary alcohol?
Use distillation with addition: the oxidising agent (acidified K₂Cr₂O₇) is heated while the alcohol is slowly added.
The aldehyde distils off as soon as it forms due to its lower boiling point, preventing further oxidation to a carboxylic acid.
How do you obtain a carboxylic acid from the full oxidation of a primary alcohol?
Heat the alcohol under reflux with excess acidified K₂Cr₂O₇.
Refluxing keeps all products in the reaction mixture, allowing the aldehyde intermediate to be further oxidised to a carboxylic acid.
True or False?
Fehling's solution gives a positive result (red precipitate) when warmed with a ketone.
False.
Ketones cannot be oxidised, so they give a negative result with Fehling's solution. Only aldehydes produce the red copper(I) oxide precipitate.
True or False?
Heating a secondary alcohol under reflux with excess acidified K₂Cr₂O₇ produces a ketone.
True.
Secondary alcohols are oxidised to ketones. Unlike aldehydes, ketones cannot be further oxidised, so refluxing does not produce a different product.
Why must acidified potassium dichromate(VI) be used to oxidise alcohols rather than the dichromate solution alone?
The reduction of dichromate ions requires H⁺ ions to proceed.
The acid (such as dilute sulfuric acid) provides these H⁺ ions, allowing Cr₂O₇^2- to act as an effective oxidising agent.

Sign up to unlock flashcards

By signing up you agree to our Terms and Privacy Policy

Previous:Organic Chemistry: HalogenoalkanesNext:Organic Chemistry: Techniques & Spectra