9701 · 13.1
Formulas, functional groups and the naming of organic compounds flashcards
Revision flashcards for Cambridge 9701 Formulas, functional groups and the naming of organic compounds (syllabus 13.1). Flip, recall, then mark a real past-paper question.
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What is a homologous series?
A series of organic compounds with the same functional group and similar chemical properties, in which successive members differ by a $CH_2$ group.
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Define 'functional group'.
An atom or group of atoms in a molecule that is responsible for its characteristic chemical reactions.
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What is the difference between a molecular formula and an empirical formula?
A molecular formula shows the actual number of atoms of each element in a molecule (e.g., $C_2H_6$ for ethane). An empirical formula shows the simplest whole-number ratio of atoms (e.g., $CH_3$ for ethane).
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What is the key difference between a structural formula and a displayed formula?
A structural formula shows the arrangement of atoms in a molecule without showing all the bonds (e.g., $CH_3CH_2OH$). A displayed formula shows every atom and every bond explicitly drawn out.
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What does a skeletal formula show?
A simplified representation where carbon chains are drawn as zig-zag lines. Vertices and line ends represent carbon atoms, and hydrogen atoms attached to carbons are not shown.
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What is the first step in naming an organic compound using IUPAC rules?
Identify the longest continuous carbon chain containing the principal functional group. This determines the 'stem' of the name.
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What is the 'lowest locant rule' in IUPAC nomenclature?
When numbering the carbon chain, start from the end that gives the functional groups and substituents the lowest possible numbers.
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What suffix is used for an alcohol (containing an -OH group)?
'-ol', for example, propan-1-ol.
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What suffix is used for a carboxylic acid (containing a -COOH group)?
'-oic acid', for example, ethanoic acid. The carbon in the COOH group is always C1.
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What suffix is used for an aldehyde (containing a -CHO group)?
'-al', for example, propanal. The carbon in the CHO group is always C1.
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What suffix is used for a ketone (containing a C=O group not at the end of a chain)?
'-one', for example, propanone. A number is needed for chains of 5 carbons or more to indicate the position of the C=O group (e.g., pentan-2-one).
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What is a common mistake when naming compounds with multiple identical substituents?
Forgetting to use prefixes like 'di-', 'tri-', or 'tetra-' (e.g., 2,2-dimethylpropane, not 2-methyl-2-methylpropane). A number is required for each substituent, even if they are on the same carbon.