Reactions alcohols undergo

Reactions of Alcohols

• Alcohol combustion can provide heat in applications such as a flaming dessert.

• Learning Objective: Ability to write balanced chemical equations for three key reactions involving alcohols:

  • Combustion

  • Dehydration

  • Oxidation

Dehydration of Alcohols

• Dehydration refers to the process where an alcohol loses a water molecule, resulting in the formation of an alkene.

• The dehydration occurs when heated in the presence of an acid catalyst.

Mechanism of Dehydration

• Alcohols undergo dehydration via the loss of a hydroxyl group (OH) and a hydrogen atom from adjacent carbon atoms.

• This results in water and an alkene as products.

Products in Dehydration

• Secondary Alcohols: Can yield both a major and a minor product

  • Major product: Formed by removing hydrogen from the carbon with fewer hydrogen atoms attached, as these hydrogen atoms are more easily removed.

Oxidation and Reduction

• Oxidation Reactions: Increase carbon-oxygen bonds.

  • Done through oxygen addition or hydrogen loss.

• Reduction Reactions: Decrease carbon-oxygen bonds.

Oxidation of First Degree Alcohols (Primary Alcohols)

• Primary alcohols oxidize to produce aldehydes; this reaction is marked with “[O]” to indicate oxidation.

• Aldehydes can further oxidize to yield carboxylic acids.

Oxidation of Second Degree Alcohols (Secondary Alcohols)

• Secondary alcohols are oxidized to produce ketones as their primary product.

Oxidation of Third Degree Alcohols (Tertiary Alcohols)

• Tertiary alcohols do not oxidize readily due to the absence of hydrogen on the carbon bonded to the alcohol group.

Chemistry Link to Health: Oxidation of Alcohol in the Body

• Methanol (Methyl alcohol)

  • Highly toxic, found in products like windshield washer fluid and paint strippers.

  • Absorbed quickly, oxidizing to formaldehyde and formic acid.

• Ethanol:

  • Acts as a depressant; causes significant mortality compared to other drugs.

  • Blood alcohol levels are measurable and vary based on consumption rate (e.g., 12-15 mg/dL/hour for social drinkers vs. 30 mg/dL/hour for alcoholics).

• In the liver, ethanol is oxidized to acetaldehyde, which is further oxidized to acetic acid, resulting in carbon dioxide and water through the citric acid cycle. These intermediates can damage liver cells.

Typical Behaviors for Alcohol Consumption

• Blood Alcohol Levels (% m/v) after consuming a specific number of drinks:

  • 1 Beer (12 oz): 0.025 - Slightly dizzy, talkative.

  • 2 Beers: 0.050 - Euphoria, loud talking.

  • 4 Beers: 0.10 - Loss of inhibition, drowsiness, legally intoxicated in most states.

  • 8 Beers: 0.20 - Intoxicated, quick to anger.

  • 12 Beers: 0.30 - Unconscious.

  • 16 to 20 Beers: 0.40 to 0.50 - Risk of coma and death.

Learning Checks

• Learning Check 1: Draw condensed structural formula for major alkene from alcohol dehydration.

• Learning Check 2: Select product for oxidation in provided scenarios.

• Learning Check 3: Identify products from subsequent reactions of alcohols.

Concept Map

• Alcohols, Phenols, Thiols, and Ethers include:

  • Alcohols, Phenols, Ethers:

    • Undergo dehydration and oxidation reactions changing to form Alkenes (from dehydration), Aldehydes, Ketones, and Carboxylic Acids (from oxidation).

  • Disulfides formed from oxidation of thiols.