Organic Chemistry: Unit Review

Carbon forms four covalent bonds, bonds strongly to other carbon atoms (making chains and rings), and forms single, double and triple bonds.

Count: 3 C, 8 H (3 + 2 + 2 + 1), 1 O → C₃H₈O.

Carbon makes four bonds; two are shown, so it has 2 H atoms.

Longest chain: 4 C (butane); methyl on C2 → 2-methylbutane.

Propane with an ethyl on C2 is CH₃CH(CH₂CH₃)CH₃. Its longest chain has 4 C, with a methyl on C2 → 2-methylbutane.

A central C with four CH₃ groups: C(CH₃)₄, which is C₅H₁₂.

Methylcyclohexane (no number needed with only one substituent).

But-1-ene (double bond starts at C1) and but-2-yne (triple bond starts at C2).

No. C1 carries two H atoms, so swapping groups on it makes the same molecule. Cis-trans isomers need two different groups on each carbon of the C=C.

An alkyne with one triple bond is CₙH₂ₙ₋₂ → C₆H₁₀.

1,3-Dimethylbenzene (also called meta-xylene).

Its six π electrons are delocalized around the ring, which makes it unusually stable. Substitution replaces an H and keeps the stable ring; addition would destroy it.

C₆H₅–CH₃ → C₇H₈.

Three: pentane, 2-methylbutane and 2,2-dimethylpropane.

Pentane (about 36 °C) > 2-methylbutane (about 28 °C) > 2,2-dimethylpropane (about 10 °C). More branching makes molecules more compact, with less surface contact, so the London forces are weaker.

They are non-polar with only London forces, so they cannot form hydrogen bonds with water; water molecules attract each other more strongly than they attract the hydrocarbon.

2-Bromopropane. Markovnikov's rule: the H adds to the carbon of the C=C that already has more H atoms, and Br adds to the other carbon.

C₃H₈ + 5O₂ → 3CO₂ + 4H₂O.

Hex-1-ene decolourizes the orange-brown bromine water quickly (addition across C=C). Hexane does not react quickly without UV light, so the colour stays.

CH₃CH₃ + Cl₂ → CH₃CH₂Cl + HCl, a substitution reaction.

Propan-2-ol, a secondary alcohol (the C bearing –OH is bonded to two other carbons).

Elimination (dehydration) gives mainly but-2-ene (plus some but-1-ene) and water.

Ethanol molecules form hydrogen bonds through their O–H groups; chloroethane has only dipole-dipole and London forces.

Methoxyethane (common name: ethyl methyl ether).

Methoxymethane (dimethyl ether), CH₃OCH₃: same formula C₂H₆O, different functional group.

Ethers have no O–H bond, so their molecules cannot hydrogen-bond to each other (they can accept H-bonds from water, which helps solubility).

Propanal (an aldehyde) and butan-2-one (a ketone, also called butanone).

Propanone; the solution changes from orange to green as Cr₂O₇²⁻ is reduced to Cr³⁺.

It is a tertiary alcohol: the carbon bearing the –OH has no H atom to remove, so it cannot form C=O without breaking C–C bonds.

Propanoic acid.

The –COOH group has both a C=O and an O–H, so acid molecules form two hydrogen bonds with each other (dimers), stronger attraction than in the alcohol.

CH₃COOH + NaHCO₃ → CH₃COONa + H₂O + CO₂ (sodium ethanoate; the fizzing is CO₂).

Ethyl ethanoate: the ethyl part comes from the alcohol, the ethanoate part from ethanoic acid.

Butanoic acid + methanol, with concentrated sulfuric acid as the catalyst (heated).

Sodium methanoate + ethanol (base hydrolysis, also called saponification).

Ethanamine, a primary amine (one carbon group on N).

A secondary amine: N-methylmethanamine (dimethylamine).

N-methylethanamide (CH₃CONHCH₃) + water.

The lone pair on nitrogen can accept an H⁺ ion, forming an ammonium ion.

Butane (London only) < propanal (dipole-dipole) < propan-1-ol (one H-bonding group) < ethanoic acid (two H-bonds per molecule, dimers).

Yes. C2 has four different groups: H, OH, CH₃ and CH₂CH₃, so the molecule and its mirror image cannot be superimposed.

Ethanol. Both can hydrogen-bond with water, but hexan-1-ol's long non-polar chain outweighs its single –OH group.

Elimination (dehydration): a small molecule is removed and a C=C forms.

Hydrolysis: water breaks the ester link.

1. Hydration: ethene + H₂O (acid catalyst) → ethanol. 2. Oxidation: ethanol + excess acidified KMnO₄ or K₂Cr₂O₇, heated → ethanoic acid.

Esterification, a condensation reaction (water is released).

Propene; addition polymerization (the C=C opens; no small molecule is lost).

Addition: monomers have a C=C; no by-product. Condensation: monomers have two functional groups each; a small molecule (usually water) is released at each link.

Hexane-1,6-diamine and hexanedioic acid, joined by amide links.

Hazard is the potential to cause harm; risk is the chance harm actually happens, which depends on hazard and exposure.

It is not broken down or excreted, so it builds up in fatty tissue (bioaccumulation); each predator eats many prey, so concentration rises at each level (biomagnification).

Example: "Bring a reusable bottle to school every day instead of buying bottled water, and tally the bottles saved each week for two months." Any specific, measurable, realistic action is acceptable.