Organic Chemistry, Biochemistry, and Environmental Chemistry
What Domain VI Tests
This domain spans organic functional groups and reactions, the major biomolecules, and environmental chemistry. Expect questions that identify a functional group from a structure, predict properties such as solubility or boiling point, recognize condensation and hydrolysis, and connect human activity to atmospheric or water-quality consequences.
Core Rules and Concepts
- Functional groups: alcohols (–OH), ethers (C–O–C), aldehydes (–CHO), ketones (C=O), carboxylic acids (–COOH), esters (–COO–), amines (–NH₂), and amides (–CONH–). Carboxylic acids are more acidic than alcohols; esters form by Fischer esterification.
- Isomers have the same molecular formula but different structures. Structural isomers differ in connectivity; stereoisomers differ in spatial arrangement (cis–trans, enantiomers).
- Organic reactions: substitution replaces one group with another; addition adds atoms across a double or triple bond; elimination removes atoms to form a multiple bond; oxidation of a primary alcohol gives an aldehyde then a carboxylic acid, while a secondary alcohol gives a ketone.
- Biochemistry: carbohydrates are polyhydroxy aldehydes or ketones; proteins are amino acid polymers joined by peptide bonds; lipids are hydrophobic and include triglycerides; nucleic acids are nucleotide polymers. Enzymes are biological catalysts that lower activation energy and are sensitive to pH and temperature.
- Environmental chemistry: greenhouse gases absorb infrared radiation; CFCs release chlorine radicals that destroy stratospheric ozone; acid rain comes from SO₂ and NOₓ; eutrophication follows excess nitrogen and phosphorus; photochemical smog involves NOₓ and volatile organic compounds.
Worked Example
Name CH₃CH(OH)CH₃, identify its functional group, and predict the organic product of its oxidation. Reasoning: the longest chain has three carbons, and the –OH is on carbon 2, so the name is propan-2-ol (isopropyl alcohol). It is a secondary alcohol because the carbon bearing –OH is attached to two other carbons. Oxidation of a secondary alcohol produces a ketone; here the product is propanone (acetone). Further oxidation does not readily give a carboxylic acid without breaking the carbon chain.
Traps That Cost Marks
- Confusing aldehydes and ketones; only aldehydes are easily oxidized by mild reagents such as Tollens' reagent.
- Naming a carboxylic acid as an alcohol because both contain oxygen and hydrogen.
- Assuming all fats are unhealthy or all polymers are synthetic; biochemistry and environmental contexts include natural polymers and essential lipids.
- Treating ozone depletion and greenhouse warming as the same process; they involve different gases and different atmospheric regions.
- Forgetting that enzymes do not change the equilibrium constant; they speed attainment of equilibrium.