Define systematic nomenclature

Systematic nomenclature is a naming system for organic compounds where the stem indicates the length of the longest carbon chain and prefixes or suffixes identify functional groups and substituents.

What stem is used for an organic compound whose longest carbon chain contains 5 carbons?

The stem is pent- , giving rise to names such as pentane.

The general formula for the alkanes is .......... For pentane (n = 5) the molecular formula is ..........

The general formula for the alkanes is C n H 2n+2 . For pentane (n = 5) the molecular formula is C 5 H 12 .

True or False? Carbon atoms in the longest chain are always numbered from the end that gives substituents the highest possible locant numbers.

False. The chain is numbered from the end that gives substituents the lowest possible locant numbers.

Define skeletal formula

A skeletal formula is a simplified displayed formula where all carbon and hydrogen atoms in the backbone are removed, leaving only bonds as lines; heteroatoms and functional-group hydrogens (e.g. –OH) are shown explicitly.

What is the difference between a displayed formula and a structural formula?

A displayed formula shows every atom and every bond explicitly in 2D; a structural formula shows how atoms are grouped around each carbon but does not draw every bond individually.

True or False? When multiple different alkyl side-chains are present, they are listed in order of increasing chain length in the IUPAC name.

False. Multiple different alkyl side-chains are listed in alphabetical order in the IUPAC name.

Define homologous series

A homologous series is a group of organic compounds that share the same functional group and general formula, with each successive member differing by –CH 2 –.

True or False? Members of the same homologous series have identical physical properties.

False. Members share similar chemical properties, but physical properties such as boiling point change gradually as the chain length increases.

How does an aliphatic compound differ from an aromatic compound?

An aliphatic compound contains carbon and hydrogen joined in straight chains, branched chains or non-aromatic rings; an aromatic compound contains a benzene ring.

The general formula for the alkenes is .......... . The molecular formula for but-1-ene (n = 4) is ..........

The general formula for the alkenes is C n H 2n . The molecular formula for but-1-ene (n = 4) is C 4 H 8 .

Define functional group

A functional group is a specific atom or group of atoms within a molecule that is responsible for its characteristic chemical reactions and determines the compound's properties.

What distinguishes a saturated organic compound from an unsaturated one?

A saturated compound contains only single carbon–carbon bonds; an unsaturated compound contains at least one carbon–carbon bond that is not single, such as C=C or C≡C.

True or False? An alicyclic compound is a type of aliphatic compound arranged in non-aromatic rings.

True. An alicyclic compound is arranged in non-aromatic rings and may have side chains, making it a subtype of aliphatic compounds.

Define structural isomers

Structural isomers are compounds that have the same molecular formula but different structural formulae , giving them different arrangements of atoms.

What are the three types of structural isomerism?

Chain isomerism Positional isomerism Functional group isomerism

True or False? Chain isomers arise when the same functional group is located on different carbon atoms within the same chain length.

False. That describes positional isomerism. Chain isomers differ in the length of the longest carbon chain , caused by branching.

Butan-1-ol and .......... are positional isomers because the hydroxyl group is on different .......... atoms.

Butan-1-ol and butan-2-ol are positional isomers because the hydroxyl group is on different carbon atoms.

Define functional group isomerism

Functional group isomerism is a type of structural isomerism where compounds share the same molecular formula but contain different functional groups , resulting in very different chemical properties.

True or False? Structural isomers must have the same molecular formula.

True. By definition, structural isomers share the same molecular formula but differ in their structural arrangement.

When deducing structural isomers, what should you check first to determine which type of isomerism applies?

First check whether different functional groups are possible (functional group isomerism), then whether the chain length can vary (chain isomerism) and finally whether a functional group can be on different carbon atoms (positional isomerism).

Define homolytic fission

Homolytic fission is the breaking of a covalent bond so that each atom takes one electron, forming two radicals : reactive species each carrying an unpaired electron (shown as •).

True or False? Heterolytic fission always produces two radicals.

False. Heterolytic fission produces a positive ion and a negative ion ; the more electronegative atom takes both electrons from the bond.

What does a double-headed curly arrow represent in a reaction mechanism?

A double-headed curly arrow represents the movement of an electron pair ; it always starts from an electron-rich site (a lone pair or a covalent bond) and points toward an electron-poor site.

In a reaction mechanism, a curly arrow must start from a .......... or a .......... and must point toward an area of ..........

In a reaction mechanism, a curly arrow must start from a lone pair or a covalent bond and must point toward an area of positive charge .

A radical is a reactive chemical species that contains an unpaired electron , represented by a dot (•), formed during homolytic fission of a covalent bond.

When is a single-headed (half-arrow) curly arrow used in a mechanism?

A single-headed curly arrow is used when a single electron moves, such as during homolytic fission or in radical termination steps.

True or False? Curly arrows are used to show electron movement in addition, substitution and elimination reactions.

True. Curly arrows feature in all three reaction types: addition , substitution and elimination reactions.

A LevelChemistryOCRFlashcards4. Core Organic ChemistryBasic Concepts

Basic Concepts (OCR A Level Chemistry A): Flashcards

Exam code: H432

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Define systematic nomenclature

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Define systematic nomenclature
Systematic nomenclature is a naming system for organic compounds where the stem indicates the length of the longest carbon chain and prefixes or suffixes identify functional groups and substituents.
What stem is used for an organic compound whose longest carbon chain contains 5 carbons?
The stem is pent-, giving rise to names such as pentane.
The general formula for the alkanes is .......... For pentane (n = 5) the molecular formula is ..........
The general formula for the alkanes is C_nH_2n+2. For pentane (n = 5) the molecular formula is C₅H₁₂.
True or False?
Carbon atoms in the longest chain are always numbered from the end that gives substituents the highest possible locant numbers.
False.
The chain is numbered from the end that gives substituents the lowest possible locant numbers.
Define skeletal formula
A skeletal formula is a simplified displayed formula where all carbon and hydrogen atoms in the backbone are removed, leaving only bonds as lines; heteroatoms and functional-group hydrogens (e.g. –OH) are shown explicitly.
What is the difference between a displayed formula and a structural formula?
A displayed formula shows every atom and every bond explicitly in 2D; a structural formula shows how atoms are grouped around each carbon but does not draw every bond individually.
True or False?
When multiple different alkyl side-chains are present, they are listed in order of increasing chain length in the IUPAC name.
False.
Multiple different alkyl side-chains are listed in alphabetical order in the IUPAC name.
Define homologous series
A homologous series is a group of organic compounds that share the same functional group and general formula, with each successive member differing by –CH₂–.
True or False?
Members of the same homologous series have identical physical properties.
False.
Members share similar chemical properties, but physical properties such as boiling point change gradually as the chain length increases.
How does an aliphatic compound differ from an aromatic compound?
An aliphatic compound contains carbon and hydrogen joined in straight chains, branched chains or non-aromatic rings; an aromatic compound contains a benzene ring.
The general formula for the alkenes is ........... The molecular formula for but-1-ene (n = 4) is ..........
The general formula for the alkenes is C_nH_2n. The molecular formula for but-1-ene (n = 4) is C₄H₈.
Define functional group
A functional group is a specific atom or group of atoms within a molecule that is responsible for its characteristic chemical reactions and determines the compound's properties.
What distinguishes a saturated organic compound from an unsaturated one?
A saturated compound contains only single carbon–carbon bonds; an unsaturated compound contains at least one carbon–carbon bond that is not single, such as C=C or C≡C.
True or False?
An alicyclic compound is a type of aliphatic compound arranged in non-aromatic rings.
True.
An alicyclic compound is arranged in non-aromatic rings and may have side chains, making it a subtype of aliphatic compounds.
Define structural isomers
Structural isomers are compounds that have the same molecular formula but different structural formulae, giving them different arrangements of atoms.
What are the three types of structural isomerism?
1. Chain isomerism
2. Positional isomerism
3. Functional group isomerism
True or False?
Chain isomers arise when the same functional group is located on different carbon atoms within the same chain length.
False.
That describes positional isomerism. Chain isomers differ in the length of the longest carbon chain, caused by branching.
Butan-1-ol and .......... are positional isomers because the hydroxyl group is on different .......... atoms.
Butan-1-ol and butan-2-ol are positional isomers because the hydroxyl group is on different carbon atoms.
Define functional group isomerism
Functional group isomerism is a type of structural isomerism where compounds share the same molecular formula but contain different functional groups, resulting in very different chemical properties.
True or False?
Structural isomers must have the same molecular formula.
True.
By definition, structural isomers share the same molecular formula but differ in their structural arrangement.
When deducing structural isomers, what should you check first to determine which type of isomerism applies?
First check whether different functional groups are possible (functional group isomerism), then whether the chain length can vary (chain isomerism) and finally whether a functional group can be on different carbon atoms (positional isomerism).
Define homolytic fission
Homolytic fission is the breaking of a covalent bond so that each atom takes one electron, forming two radicals: reactive species each carrying an unpaired electron (shown as •).
True or False?
Heterolytic fission always produces two radicals.
False.
Heterolytic fission produces a positive ion and a negative ion; the more electronegative atom takes both electrons from the bond.
What does a double-headed curly arrow represent in a reaction mechanism?
A double-headed curly arrow represents the movement of an electron pair; it always starts from an electron-rich site (a lone pair or a covalent bond) and points toward an electron-poor site.
In a reaction mechanism, a curly arrow must start from a .......... or a .......... and must point toward an area of ..........
In a reaction mechanism, a curly arrow must start from a lone pair or a covalent bond and must point toward an area of positive charge.
Define radical
A radical is a reactive chemical species that contains an unpaired electron, represented by a dot (•), formed during homolytic fission of a covalent bond.
When is a single-headed (half-arrow) curly arrow used in a mechanism?
A single-headed curly arrow is used when a single electron moves, such as during homolytic fission or in radical termination steps.
True or False?
Curly arrows are used to show electron movement in addition, substitution and elimination reactions.
True.
Curly arrows feature in all three reaction types: addition, substitution and elimination reactions.

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