"Introduction to organic nomenclature: monofunctional compounds"

Natural gas for cooking is methane, $\text{CH}_4$; tap water is $\text{H}_2\text{O}$; a lighter contains butane, $\text{C}_4\text{H}_{10}$; salt is $\text{NaCl}$ and rubbing alcohol is ethanol, $\text{C}_2\text{H}_6\text{O}$.

1. a) State which of these substances are organic compounds and which are not.
2. b) Explain in your own words which element is the "backbone" of organic chemistry.

Name these four hydrocarbons:

The figure shows the molecular models of all four.

1. a) $\text{CH}_4$
2. b) $\text{C}_2\text{H}_6$
3. c) $\text{C}_3\text{H}_8$
4. d) $\text{C}_4\text{H}_{10}$

1. e) Explain what the prefix (meth-, eth-, prop-, but-) indicates and what the suffix -ane indicates.

All alkanes follow the general formula $\text{C}_n\text{H}_{2n+2}$, where $n$ is the number of carbon atoms.

1. a) Check that this holds true for methane ($n = 1$) and for butane ($n = 4$).
2. b) Work out the molecular formula of the alkane with $5$ carbon atoms, called pentane.

Fruit naturally releases a gas that accelerates its ripening: ethene, $\text{C}_2\text{H}_4$.

1. a) What type of bond joins its two carbon atoms: single, double or triple?
2. b) Which family does it belong to?

Alkenes follow the general formula $\text{C}_n\text{H}_{2n}$ and alkynes, $\text{C}_n\text{H}_{2n-2}$.

1. a) Work out the molecular formula of propene (an alkene with $3$ carbon atoms).
2. b) Work out that of propyne (an alkyne with $3$ carbon atoms).
3. c) Explain why ethene cannot have the formula $\text{C}_2\text{H}_6$.

Two compounds with $4$ carbon atoms have formulas $\text{C}_4\text{H}_{10}$ and $\text{C}_4\text{H}_8$.

1. a) Using the general formulas, state which is an alkane and which is an alkene.
2. b) Name the alkane.
3. c) Could either of the two be an alkyne? Justify your answer using the general formula $\text{C}_n\text{H}_{2n-2}$.

Methanol, $\text{CH}_3\text{OH}$, is used as fuel in some model engines and ethanol, $\text{CH}_3\text{CH}_2\text{OH}$, is the alcohol in disinfectants.

1. a) What group of atoms do both formulas share?
2. b) What is this functional group called and which family do both compounds belong to?

Ethanol has the molecular formula $\text{C}_2\text{H}_6\text{O}$ and ethane, $\text{C}_2\text{H}_6$.

1. a) Explain why ethanol is not considered a hydrocarbon, even though it is so similar to ethane.
2. b) Which family does ethanol belong to and what is its functional group?

An alcohol can be imagined as an alkane in which a hydrogen atom has been replaced by an $-\text{OH}$ group.

1. a) Apply this idea to methane and write the condensed structural formula of methanol.
2. b) Do the same with ethane and write that of ethanol.
3. c) Also write the molecular formulas of both alcohols.

The sour taste of vinegar is due to acetic acid, whose IUPAC name is ethanoic acid, $\text{CH}_3\text{COOH}$.

1. a) Count how many carbon, hydrogen and oxygen atoms its molecule has and write its molecular formula (all atoms together, without separating by groups).
2. b) Indicate in the formula the $-\text{COOH}$ functional group characteristic of carboxylic acids.

Indicate the functional group of each compound and state which family it belongs to:

1. a) $\text{CH}_3\text{OH}$
2. b) $\text{CH}_3\text{CH}_2\text{OH}$
3. c) $\text{CH}_3\text{COOH}$

In the laboratory there are two bottles: one contains the alcohol with $2$ carbon atoms and the other contains the carboxylic acid with $2$ carbon atoms.

1. a) Write the condensed structural formula of each and name them according to IUPAC.
2. b) Circle the functional group in each formula and state its name.
3. c) State an everyday substance in which each one is found.