Formulas, Functional Groups & the Naming of Organic Compounds (Cambridge (CIE) A Level Chemistry): Flashcards
Exam code: 9701
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- FrontFunctional Groups
Define functional group.
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Cards in this collection (27)
Define functional group.
A functional group is an atom or group of atoms in an organic molecule that determines its characteristic chemical and physical properties.
Why do arenes prefer substitution reactions over addition reactions?
Arenes prefer substitution reactions because the delocalised π electron ring system is extremely stable. Addition reactions would disrupt this aromatic stabilisation, whereas substitution reactions maintain the delocalised ring.
True or False?
Halogenoarenes are soluble in water due to the halogen atom attached to the ring.
False.
Halogenoarenes are insoluble in water. The non-polar hydrocarbon ring means it is not energetically favourable for halogenoarene molecules to break the hydrogen bonds between water molecules.
Amines are basic due to the .......... on the nitrogen atom, which can accept a proton.
Amines are basic due to the lone pair of electrons on the nitrogen atom, which can accept a proton.
Define phenol.
A phenol is an aromatic compound containing a hydroxyl group (–OH) bonded directly to a benzene ring.
Why is the –OH group in phenol more acidic than in alcohols?
The oxygen in phenol donates one of its lone pairs into the ring's π system, increasing electron density in the ring. This weakens the O–H bond, making the hydrogen easier to donate and phenol more acidic than an alcohol.
True or False?
Amides are more basic than amines.
False.
Amides are less basic than amines because the lone pair on the nitrogen is delocalised into the adjacent C=O group, making it less available to accept a proton.
Acyl chlorides are extremely reactive and readily undergo .......... reactions in which the chlorine atom is replaced by another species.
Acyl chlorides are extremely reactive and readily undergo substitution reactions in which the chlorine atom is replaced by another species.
What structural features define an amino acid?
An amino acid contains both an amine group (–NH2) and a carboxyl group (–COOH). Most amino acids have a chiral centre and exhibit optical isomers, except for glycine.
Define skeletal formula.
A skeletal formula is a simplified structural representation of an organic molecule that shows the carbon skeleton as a zigzag, with functional groups shown explicitly and hydrogen atoms on carbon omitted.
What is the difference between a structural formula and a displayed formula?
A structural formula shows how atoms are grouped and bonded without showing all individual bonds. A displayed formula shows every bond in the molecule explicitly, including all C–H bonds.
True or False?
A general formula can be used to represent all members of a homologous series.
True.
A general formula gives the simplest algebraic expression for any member of a homologous series. For example, alkanes have the general formula CnH2n+2.
In a skeletal formula, carbon atoms are represented by .......... in a zigzag chain, and hydrogen atoms bonded to carbon are .......... .
In a skeletal formula, carbon atoms are represented by vertices/line ends in a zigzag chain, and hydrogen atoms bonded to carbon are not shown.
Define general formula.
A general formula is the simplest algebraic expression that describes the molecular formula of any member of a homologous series.
Which type of formula shows every atom and bond in a molecule?
A displayed formula shows every atom and every bond in the molecule, including all C–H bonds.
True or False?
A structural formula shows all individual C–H bonds explicitly.
False.
A structural formula groups atoms together (e.g. CH3CH2OH) without drawing every individual bond. It is the displayed formula that shows all bonds explicitly.
The four types of formula used for organic compounds are: general formula, .......... , displayed formula and skeletal formula.
The four types of formula used for organic compounds are: general formula, structural formula, displayed formula and skeletal formula.
Why are skeletal formulae particularly useful for complex organic molecules?
Skeletal formulae are useful for complex molecules because they omit carbon and hydrogen atoms on the chain, making the structure cleaner and easier to read. Functional groups and heteroatoms are still shown explicitly.
Define systematic nomenclature.
A systematic nomenclature is a standardised method of naming organic compounds based on the length of the longest carbon chain, the functional group present and the positions of substituents.
What is the first step when naming an aliphatic organic compound systematically?
Identify the longest carbon chain that contains the principal functional group. This gives the parent chain name and the base suffix.
True or False?
When numbering the carbon chain, the functional group should be given the highest possible locant.
False.
The carbon chain should be numbered so that the principal functional group has the lowest possible locant.
When two or more identical substituents are present, the prefixes .......... , tri- or tetra- are added before the substituent name.
When two or more identical substituents are present, the prefixes di-, tri- or tetra- are added before the substituent name.
Define aromatic compound.
An aromatic compound is an organic compound that contains a benzene ring with a conjugated π system of delocalised electrons.
How is the naming of aromatic compounds similar to that of aliphatic compounds?
Both use the position numbering system to indicate where substituents are located. For aromatic compounds, benzene is the parent name and substituents are numbered to give the lowest possible locants.
True or False?
Multiple substituents on a benzene ring are listed alphabetically before the parent name.
True.
Substituents on a benzene ring (and on aliphatic chains) are listed as prefixes in alphabetical order before the parent chain name.
In 2-methylchlorobenzene, the number 2 indicates the position of the .......... group relative to the .......... group.
In 2-methylchlorobenzene, the number 2 indicates the position of the methyl group relative to the chloro group.
What suffix is used in the name of an amide, and what functional group does it indicate?
The suffix -amide is used. It indicates the presence of the –CONH2 group, which contains a carbonyl (C=O) and an amine (–NH2) group.
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