Visualising Organic Chemistry Trivia Quiz

Answer: Propane

The simplest alkane molecules are those that consist of a single chain of carbon atoms surrounded by hydrogen atoms. As each carbon atom can form four single bonds (they are known as 'tetravalent'), this means that those in the middle of the chain are bonded to the two adjacent carbons and two hydrogen atoms, whilst those at the end are bonded to one carbon and three hydrogens. This gives simple alkanes a formula of C(n)H(2n+2), where 'n' is the number of carbon atoms.

In organic chemistry, 'prop' is the prefix used to refer to the number three, hence the fact that the molecule in the picture (C3H8) is called propane. Pentane and hexane are perhaps easier to read, containing five and six carbon atoms respectively, whilst methane is the simplest alkane and has the formula CH4.

Answer: Five

This simple structure may just look like the letter 'M', but is actually the skeletal formula for pentane, the simple alkane containing five carbon atoms and with formula C5H12. The way to read the skeletal formula is that each endpoint of a line represents a carbon atom, with the assumption that it is saturated with hydrogen atoms unless some other bond is indicated.

The ubiquity of the alkane functional group within many organic molecules is the reason for this convenient shorthand. An alkane chain is the 'norm', whilst other groups add new functionality.

Answer: Alkenes

The alkene functional group is defined by the carbon-carbon double bond, and thus the simplest alkene compound requires two carbon atoms. This molecule, shown in the picture, is systematically called ethene, but is more commonly referred to as ethylene. It is one of the most widely produced chemicals in the word, largely due to the fact that it can be easily polymerised into a plastic known as polyethylene, used extensively for plastic bags, bottles, and many other products.

Of the incorrect answers, one of them is itself a functional group. Alkynes are characterised by a carbon-carbon triple bond, and are also known as the acetylenes.

Answer: Ethanol

Ethanol is the primary type of alcohol found in alcoholic drinks. The percentage of pure alcohol in a drink can range from below 1% in low-alcohol beers to 98% or more in certain types of absinthe and other spirits. As well as being used for drinking, ethanol has also been used as a relatively clean fuel for cars and other vehicles, though it is more commonly found blended with gasoline than used as a standalone fuel.

Isopropyl alcohol is the simplest secondary alcohol, meaning that the OH group that defines the alcohol is not found at the end of the carbon chain. In isopropyl alcohol the group is found on the middle of three carbons, and it is therefore systematically named propan-2-ol. It is used extensively in industry, and is perhaps best known for its antiseptic properties.

Answer: Carboxylic acid

Acids are compounds which can 'donate' protons (hydrogen atoms that have lost their electron). The strength of an acid is often considered in terms of what proportion of the molecules dissociate when placed into solution, where dissociate means that the proton splits off from the parent molecule. Carboxylic acids are typically thought of as 'weaker' acids, meaning that only a small percentage of molecules dissociate. Other acids such as sulphuric or hydrochloric are significantly stronger, with almost 100% dissociation.

The carboxylic acid shown in the picture is methanoic acid, also known as formic acid. It takes this second name from the Latin word for 'ant' ('formica'), as it is commonly found as a defence mechanism in ants.

Answer: Biphenyl

The phenyl functional group differs in composition from benzene as it has the chemical formula C6H5, whilst benzene is C6H6. The lack of the sixth hydrogen atom is due to the fact that one of the carbon atoms in the ring needs to have a spare bond available to combine with the rest of the molecule in which it is found.

The chemistry of molecules containing such groups is often broadly referred to as 'aromatic' chemistry, a name that was given to the compounds before anyone knew what caused the phenomenon, and was simply based on the smell the chemicals produced.

Answer: Aldehydes

Both aldehydes and ketones (see Q8) contain a carbonyl group, a carbon atom double-bonded to an oxygen atom. The difference between the two is that in an aldehyde, the carbon that is double-bonded to the oxygen is also single-bonded to a hydrogen atom, meaning that the carbonyl group must occur at the end of a chain of carbon atoms.

Formaldehyde (the simplest aldehyde compound) has long been used as an embalming agent and fixative. However, whilst formaldehyde does cause a solidifying of bodily tissue and subsequently delays the decaying process, it does not fully prevent it and thus cannot be used for indefinite storage. Despite its widespread usage in a variety of scientific and industrial fields, formaldehyde is known to be harmful to human health and is designated as a 'known carcinogen'.

Answer: Amino

Amino acids very much reveal their functionality in their name - they contain both an amine group and a carboxylic acid group. An amine group is defined by the presence of a nitrogen atom with a lone pair of electrons, often manifested as an NH2 group attached to a carbon atom in an organic compound. Whilst all amino acids contain these two groups, they differ in the side group that is bonded to the carbon which bonds the nitrogen atom. Alanine (shown in the picture) is one of the simpler amino acid structures, featuring only an methyl (CH3) group as a side chain.

Amino acids are chained together during a process known as translation, a key step in the conversion of genetic material into functional molecules. This chain of amino acids is then folded in a precise way to form a protein, which can then carry out a specific function within a living cell.

Answer: False

Similar to aldehydes, ketones also contain a carbonyl group (carbon-oxygen double bond). However, unlike in an aldehyde, the carbon atom that is forming that oxygen bond must also be bonded to two adjacent carbon atoms. The nomenclature 'R' in a diagram such as this one does not represent an atom of a single element, but instead the presence of an organic side group of unknown composition. The use of both R and R' in this diagram indicates that there is no obligation for the two side groups to be the same.

The chemical symbol for radon is Rn, and no element is represented by the letter 'R' on its own. However, 14 elements are represented by single letters, with the earliest alphabetically being 'B' (boron) and the last 'Y' (yttrium).

Answer: Sulphur

As shown in the picture, the thiol functional group features an atom of sulphur ('S') bound to an atom of hydrogen and coming off of a hydrocarbon chain. The smell of many thiol compounds has been likened to rotten eggs, and they are added to natural gas to provide an odour to aid recognition. The picture shows ethanethiol, one of the smallest (but by no means least odorous) thiol compounds.

Of the incorrect answers, sodium has the chemical symbol 'Na', silver has the symbol 'Ag', and samarium is represented by 'Sm'.