4.2.1 - Alcohols Flashcards
What is the general formula of an alcohol?
The general formula of an alcohol is CₙH₂ₙ₊₁OH.
What is the functional group of an alcohol?
The functional group of an alcohol is the -OH (hydroxyl) group.
How do alcohols classify into primary, secondary, and tertiary alcohols?
- Primary alcohol: The -OH group is attached to a carbon atom that is bonded to only one other carbon atom.
- Secondary alcohol: The -OH group is attached to a carbon atom bonded to two other carbon atoms.
- Tertiary alcohol: The -OH group is attached to a carbon atom bonded to three other carbon atoms.
What is the difference between an alcohol and an aldehyde?
An alcohol contains a hydroxyl group (-OH), whereas an aldehyde contains a carbonyl group (C=O) with a hydrogen atom attached to the carbonyl carbon.
What are some examples of primary alcohols?
Examples of primary alcohols include ethanol (CH₃CH₂OH) and butan-1-ol (CH₃CH₂CH₂OH).
What are some examples of secondary alcohols?
Examples of secondary alcohols include propan-2-ol (CH₃CHOHCH₃) and butan-2-ol (CH₃CH(OH)CH₂CH₃).
What are some examples of tertiary alcohols?
Examples of tertiary alcohols include 2-methylpropan-2-ol (CH₃C(OH)(CH₃)₂) and 2,2-dimethylpropan-1-ol (CH₃C(OH)(CH₃)₂CH₂).
How do alcohols react with sodium?
Alcohols react with sodium metal to form alkoxide ions (R-O⁻) and hydrogen gas (H₂) as a byproduct.
Example:
2Na + 2CH₃CH₂OH → 2CH₃CH₂O⁻Na⁺ + H₂
How can alcohols be oxidized?
- Primary alcohols can be oxidized to aldehydes and then further to carboxylic acids.
- Secondary alcohols can be oxidized to ketones.
- Tertiary alcohols do not undergo oxidation easily.
What is the reagent used to oxidize primary alcohols to aldehydes?
[O] or Potassium dichromate (K₂Cr₂O₇) in acidic conditions can oxidize primary alcohols to aldehydes.
What is a common method for dehydrating alcohols?
Alcohols can be dehydrated using concentrated sulfuric acid (H₂SO₄) or phosphoric acid (H₃PO₄) at high temperatures to form alkenes.
Example:
C₂H₅OH → C₂H₄ + H₂O (ethanol → ethene)
What is the result of the reaction between alcohols and carboxylic acids?
Alcohols react with carboxylic acids in the presence of a catalyst to form esters and water.
Example:
CH₃CH₂OH + CH₃COOH → CH₃COOCH₂CH₃ + H₂O (ethanol + ethanoic acid → ethyl ethanoate + water)
How can alcohols be classified based on their reactivity with oxidizing agents?
- Primary alcohols: Oxidize to aldehydes (with mild oxidants) or carboxylic acids (with stronger oxidants).
- Secondary alcohols: Oxidize to ketones.
- Tertiary alcohols: Do not oxidize easily.
What is the functional group test for alcohols?
Alcohols can be tested by reacting with sodium or forming esters with carboxylic acids. Alternatively, the Lucas test (with zinc chloride and hydrochloric acid) distinguishes between primary, secondary, and tertiary alcohols based on their rate of reaction.
What is the Lucas test, and how does it work?
The Lucas test involves reacting alcohol with Lucas reagent (ZnCl₂ in HCl).
- Tertiary alcohols react immediately.
- Secondary alcohols react after a few minutes.
- Primary alcohols show little to no reaction.
How can alcohols be used in the production of fuels?
Alcohols, especially ethanol, can be used as an alternative fuel in biofuels. They are produced by the fermentation of sugars and are used in gasoline blends.
What is the mechanism of the oxidation of alcohols?
In the oxidation of alcohols, the alcohol loses electrons (is oxidized), and the oxidizing agent gains electrons. The hydroxyl group (-OH) is replaced by a double bond to oxygen (forming a carbonyl group, C=O).
What is the difference between an alcohol and an ether?
Alcohols have a hydroxyl group (-OH), while ethers have an oxygen atom bonded to two carbon atoms (R-O-R’).
What is the use of phenols, and how do they differ from alcohols?
Phenols are similar to alcohols but have the hydroxyl group attached to a benzene ring. They are more acidic than alcohols due to the resonance stability of the phenoxide ion.
What are the products of the combustion of alcohols?
The complete combustion of alcohols produces carbon dioxide (CO₂) and water (H₂O).
Example:
C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O (ethanol combustion)
