Organic chemistry flashcards

Topic 7: Organic chemistry

Hydrocarbon

A compound of hydrogen and carbon only.

Homologous series

A family of compounds with the same general formula and the same functional group.

Alkanes: general formula and the first four

CₙH₂ₙ₊₂ (saturated, only single C–C bonds). Methane, ethane, propane, butane.

How does fractional distillation separate crude oil?

Crude oil is heated to evaporate it; the vapour rises up a column that is hot at the bottom and cooler at the top; each hydrocarbon condenses at a level below its boiling point. Long chains collect low, short chains high.

How do boiling point, viscosity and flammability change as hydrocarbon molecules get larger?

Boiling point increases, viscosity increases, flammability decreases.

Cracking: what it is, and the two methods

Breaking large hydrocarbons into smaller, more useful molecules (smaller alkanes + alkenes). Catalytic: vapour over a hot catalyst. Steam: vapour mixed with steam at a very high temperature.

Test for an alkene

Shake with bromine water: orange → colourless. An alkane leaves it orange.

What forms when an alcohol reacts with sodium, and with an oxidising agent?

Sodium: fizzing, hydrogen given off. Oxidising agent: a carboxylic acid (propanol → propanoic acid).

Ethanoic acid + ethanol (acid catalyst) gives…

The ester ethyl ethanoate, and water.

Addition polymerisation

Many alkene monomers join as the C=C opens to C–C. Nothing else forms, so the repeating unit has the same atoms as the monomer. Example: ethene → poly(ethene).

Condensation polymerisationHigher

Monomers each with two functional groups join, losing a small molecule (usually water) at each link. Example: ethanediol + hexanedioic acid → a polyester + water.

Amino acids and proteinsHigher

An amino acid has two different functional groups (–NH₂ and –COOH), such as glycine, H₂NCH₂COOH. Amino acids join by condensation polymerisation to make polypeptides; different amino acids make proteins.