VCE Unit 4: Organic Compounds and Reactions

Reactions of Organic Compounds

• Alkanes undergo substitution reactions, while alkenes undergo addition reactions.
• Substitution reactions occur when an atom or group of atoms replaces another atom or group of atoms, forming a new substance.

Types of Organic Reactions

• Substitution reactions involve the replacement of an atom or group of atoms with another atom or group of atoms.
• Substitution reactions can occur through free radicals, which require initiation, propagation, and termination steps.
• Alkanes are non-polar and hence not very reactive, but free radicals can initiate substitution reactions.
• Examples of substitution reactions include the formation of haloalkanes and the formation of alcohols from haloalkanes.

Addition Reactions

• Addition reactions occur when atoms or groups add across a double or triple bond, forming a new substance.
• Unsaturated hydrocarbons, such as alkenes and alkynes, are very reactive and undergo addition reactions.
• Addition reactions can occur with or without a catalyst, and examples include the addition of hydrogen chloride to an alkene and the addition of bromine to an alkene.

Pathways to New Products

• New products can be formed through substitution and addition reactions.
• Examples include the formation of secondary alcohols, ketones, and amines.
• Condensation reactions are also important in the formation of new products.

Oxidation of Alcohols

• Oxidation of alcohols occurs when an alcohol is oxidized in the presence of an oxidizing agent and a catalyst.
• Primary alcohols can be oxidized to aldehydes and then to carboxylic acids, while secondary alcohols can be oxidized to ketones.
• Tertiary alcohols cannot be oxidized.
• Strong oxidizing agents, such as permanganate and dichromate ions, can be used to oxidize alcohols.

Condensation Reactions

• Condensation reactions occur when two molecules combine, releasing water.
• Examples include the formation of amides (peptide links) and esters (esterification).
• Condensation reactions are important in the formation of biomolecules such as proteins, carbohydrates, and lipids.

Hydrolysis Reactions

• Hydrolysis reactions occur when water is used to break a larger molecule into smaller products.
• Hydrolysis reactions are the reverse of condensation reactions.
• Examples include the hydrolysis of proteins, carbohydrates, and lipids.

Biomolecules

• Biomolecules are molecules with biological function and include proteins, carbohydrates, and lipids.
• Proteins are formed through condensation reactions between amino acids and are important for structure, function, and regulation in the body.
• Carbohydrates are formed through condensation reactions between monosaccharides and are important for energy storage and structure.
• Lipids are formed through condensation reactions between glycerol and fatty acids and are important for energy storage and structure.

Condensation Reactions in Biomolecules

• Proteins are formed through condensation reactions between amino acids.
• Carbohydrates are formed through condensation reactions between monosaccharides.
• Lipids are formed through condensation reactions between glycerol and fatty acids.

Hydrolysis Reactions in Biomolecules

• Proteins can be broken down through hydrolysis reactions into peptides and amino acids.
• Carbohydrates can be broken down through hydrolysis reactions into disaccharides and monosaccharides.
• Lipids can be broken down through hydrolysis reactions into glycerol and fatty acids.### Hydrolysis of Carbohydrates
• A polysaccharide composed of glucose molecules (C6H12O6) has a molar mass of 3.2418 × 104 g mol–1.
• When the polysaccharide is hydrolyzed, 200 glucose monomers will be produced.

Hydrolysis Reactions of Biomolecules

• Triglycerides are broken down into glycerol and fatty acids during hydrolysis.
• One water molecule is needed for each ester link that is broken.
• The reaction requires a biological catalyst.

Efficiency of Reactions

• Efficiency of reactions can be measured by atom economy.
• Atom economy is a measure of how many of the atoms in the reactants end up in the desired product.
• Efficiency of reactions can also be measured by percentage yield.

Atom Economy

• Atom economy is calculated by dividing the molar mass of the desired product by the molar mass of the reactants and multiplying by 100%.

Percentage Yield

• The percentage yield is the amount of product produced in a reaction, expressed as a percentage.
• Theoretical yield is the maximum amount of product that can be formed using the stoichiometric ratios and assuming 100% conversion.
• Actual yield is the amount of product obtained experimentally.

Example Questions

• Calculate the percentage atom economy in the production of ethanol from chloroethane.
• Calculate the percentage yield of the combustion reaction of propene.
• Calculate the percentage yield of ethanol for the fermentation reaction of glucose.

Multistep Synthesis

• The overall yield of the product of a multistep reaction is found by multiplying the yields of each step and expressing as a percentage.

Pathways to New Products

• Secondary alcohols can be converted into ketones through oxidation.
• Primary amines can be converted into amides through condensation.
• Alkylammonium fluoride salts can be used to convert fluoroethane into ethylethanoate.

Reagents and Conditions

• Different reagents and conditions can be used to produce different products.
• Understanding the reagents and conditions required for different reactions is important in producing new products.