Cycloalkanes for SQA National 5 Chemistry

This page covers the following topics:

1. Formulae and solubility
2. First five
3. Molecular formula

Cycloalkanes are hydrocarbons that consist of a ring of carbons with single carbon-carbon bonds. As they contain only carbon and hydrogen they are also not very soluble in water. They generally have slightly higher boiling points than alkanes.

The first 4 clycloalkanes have a different number of carbons to the first 4 alkanes as there MUST be a carbon ring. The minimum number of carbons needed to complete a ring is 3.

Molecular formula shows the number and type of atoms present in a molecule, remember that for alkenes they will follow the general formula from before.

1

What is the general formula of cycloalkanes?

CnH2n

2

What is the name of the cycloalkane with the shortest possible carbon chain (the first cycloalkane)?

There must be at least 3 carbons to form a ring, thus it will have 3 carbon atoms.

cyclopropane

3

What is the molecular formula of cyclohexane?

C₆H₁₂

4

The boiling point point of pentane is 36°C, estimate what the boiling point of cyclopentane is.

49°C (accept anything between 37° and 67°C)

5

How does solubility of cycloalkanes change with chain length?

Shorter cycloalkanes are slightly more soluble than longer chain alkenes

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