What is a general formula?

An algebraic formula for a homologous series, for example CₙH₂ₙ₊₂ for alkanes.

What is a displayed formula?

A formula that shows every atom and every bond.

What is a skeletal formula?

A simplified formula showing the carbon skeleton as lines, with functional groups, but no C or H labels on carbons.

What is a homologous series?

A series of compounds containing the same functional group.

How do you number a carbon chain?

From the end that gives the lowest locant to the functional group, then to substituents.

In what order are substituents named?

Alphabetical order, ignoring di-, tri- and tetra-.

Nomenclature and formulaeAQA A-Level Chemistry: Flashcards

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What is an empirical formula?

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What is an empirical formula?: The simplest whole-number ratio of atoms of each element in a compound.
What is the empirical formula of hexane?: C₃H₇
What is a general formula?: An algebraic formula for a homologous series, for example CₙH₂ₙ₊₂ for alkanes.
What is a displayed formula?: A formula that shows every atom and every bond.
What is a skeletal formula?: A simplified formula showing the carbon skeleton as lines, with functional groups, but no C or H labels on carbons.
What is a homologous series?: A series of compounds containing the same functional group.
What is the stem for a five-carbon chain?: pent-
What suffix shows an alcohol?: -ol
How do you number a carbon chain?: From the end that gives the lowest locant to the functional group, then to substituents.
In what order are substituents named?: Alphabetical order, ignoring di-, tri- and tetra-.
Name CH₃CH(CH₃)CH₂CH₂CH₃.: 2-methylpentane
Name CH₃CHBrCH₂Cl.: 2-bromo-1-chloropropane
Name (CH₃)₃CCl.: 2-chloro-2-methylpropane
What prefix shows a ring?: cyclo-

Exam questions on Nomenclature and formulae

Petrol contains a mixture of alkanes. A chemist analyses one branched alkane with the structural formula CH₃CH(CH₃)CH₂CH₂CH₃ and compares it with the straight-chain alkane that has the same number of carbon atoms.
State what is meant by a homologous series.2 marks
A solvent supplier labels its bottles with systematic names. The stock list includes an alcohol with the structural formula CH₃CH(OH)CH₂CH₃, a dihalogenoalkane with the structural formula CH₃CHBrCH₂Cl, and a halogenoalkane with the structural formula (CH₃)₃CCl.
Write the structural formula of 2-chloro-2-methylpropane and give its molecular formula.2 marks
A stock room holds three hydrocarbons. Compound P has the structural formula CH₃CH=CHCH₂CH₃. Compound Q has the structural formula CH₂=C(CH₃)CH₂CH₃. Compound R is a ring of five carbon atoms joined by single bonds, in which one carbon atom carries a methyl group.
Give the IUPAC names of P, Q and R.3 marks

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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).