Introduction to Organic Chemistry (AQA A Level Chemistry): Flashcards
Exam code: 7405
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What is catenation in organic chemistry?
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Cards in this collection (35)
What is catenation in organic chemistry?
A calorimeter is a device used to measure the heat energy change during a chemical or physical process. The temperature change of a known mass of water (or another substance) is used to calculate the energy transferred.
True or False?
Ethanol is a hydrocarbon because it contains only carbon and hydrogen atoms.
False.
Ethanol contains carbon, hydrogen, and oxygen. Hydrocarbons contain only carbon and hydrogen atoms; ethanol is not a hydrocarbon.
A homologous series is a group of organic compounds that have the same .......... group and the same .......... formula. Each successive member differs by .......... .
A homologous series is a group of organic compounds that have the same functional group and the same general formula. Each successive member differs by CH2.
What is a functional group?
A mean bond enthalpy is the average enthalpy change when one mole of a specific bond is broken homolytically in the gas phase, calculated as a mean across a range of different compounds containing that bond.
State the functional group present in each: halogenoalkane, alcohol, and carboxylic acid.
Halogenoalkane: R-X (where X = F, Cl, Br, or I)
Alcohol: R-OH
Carboxylic acid: R-COOH
A hydrocarbon is a compound made up of .......... and .......... atoms only. Alkanes, alkenes, and cycloalkanes are all examples of .......... .
A hydrocarbon is a compound made up of carbon and hydrogen atoms only. Alkanes, alkenes, and cycloalkanes are all examples of hydrocarbons.
True or False?
Members of the same homologous series have similar chemical properties but gradually changing physical properties.
True.
All members share the same functional group and thus have similar reactivity. Physical properties such as boiling point and density change gradually as molecular size increases up the series.
What is a skeletal formula?
A Hess's law is the law stating that the total enthalpy change for a reaction is independent of the route taken, provided the initial and final states are the same.
The .......... formula shows all atoms by their symbols and all bonds. The .......... formula shows how atoms are bonded to each carbon. The .......... formula shows the simplest whole number ratio of atoms.
The displayed formula shows all atoms by their symbols and all bonds. The structural formula shows how atoms are bonded to each carbon. The empirical formula shows the simplest whole number ratio of atoms.
True or False?
The empirical formula of ethanoic acid (C2H4O2) is CH2O.
True.
The empirical formula gives the simplest whole number ratio of atoms. Dividing C2H4O2 by 2 gives the ratio C:H:O = 1:2:1, so the empirical formula is CH2O.
What is a general formula in organic chemistry?
General formula uses letters and numbers to represent any member of a homologous series. For example, the general formula for alkanes is CnH2n+2.
Substituting values of n gives the molecular formula of each individual member of the series.
The molecular formula of ethanoic acid is ........... Its empirical formula is ........... These differ because the molecular formula shows the .......... number of each atom, whereas the empirical formula shows the .......... ratio.
The molecular formula of ethanoic acid is C2H4O2. Its empirical formula is CH2O. These differ because the molecular formula shows the actual number of each atom, whereas the empirical formula shows the simplest whole number ratio.
True or False?
In a displayed formula, C-H bonds can be represented as sticks (lines without showing the H).
False.
A displayed formula must show every atom by its symbol and every bond. Writing sticks without H atoms is penalised in AQA exams.
What is the difference between a structural formula and a displayed formula?
A structural formula shows the atoms bonded to each carbon atom in sequence but does not show every bond explicitly. A displayed formula shows every atom by symbol and every bond, including all C-H bonds.
What does the stem of an organic compound name indicate?
The stem indicates the number of carbon atoms in the longest carbon chain. For example, meth- = 1 carbon, eth- = 2, prop- = 3, but- = 4, pent- = 5, hex- = 6.
In systematic nomenclature, carbon atoms are numbered from the end that gives the .......... possible numbers. Side chains are named by adding .......... to the alkane stem and are listed in .......... order if more than one type is present.
In systematic nomenclature, carbon atoms are numbered from the end that gives the lowest possible numbers. Side chains are named by adding -yl to the alkane stem and are listed in alphabetical order if more than one type is present.
True or False?
A compound with two identical methyl branches should have "di" included before the group name in its IUPAC name.
True.
The prefixes di- (two), tri- (three), and tetra- (four) are used before repeated group names. Numbers are separated by commas and numbers from words by hyphens.
What is an alkyl group?
A Born–Haber cycle is an application of Hess's law used to calculate lattice enthalpy by constructing an energy cycle linking the formation of an ionic compound from its elements with other known enthalpy changes.
Name the following compound: CH3CH(CH3)CH2CH3
The longest chain has .......... carbons. The methyl branch is on carbon ........... The name is .......... .
The longest chain has 4 carbons. The methyl branch is on carbon 2. The name is 2-methylbutane.
True or False?
The IUPAC name for a compound with a hydroxyl group on the second carbon of a four-carbon chain is "but-2-ol".
False.
The correct IUPAC name is butan-2-ol. AQA penalises non-IUPAC forms such as "but-2-ol", "2-butanol", or "butane-2-ol".
Give the IUPAC suffix for each: alkene, alcohol, aldehyde, carboxylic acid.
Alkene: -ene
Alcohol: -ol
Aldehyde: -al
Carboxylic acid: -oic acid
What are structural isomers?
Structural isomers are compounds that have the same molecular formula but different structural formulae. They are not defined by "same empirical formula" or "same chemical formula" — AQA penalises both of these.
True or False?
Pentane and 2,2-dimethylpropane are chain isomers because they have the same molecular formula but different longest carbon chains.
True.
Both have molecular formula C5H12. Pentane has a 5-carbon chain; 2,2-dimethylpropane has a 3-carbon chain with two methyl branches. The difference in chain length makes them chain isomers.
The three types of structural isomerism are .......... isomerism (different chain length), .......... isomerism (different position of functional group) and .......... group isomerism (different functional groups with the same molecular formula).
The three types of structural isomerism are chain isomerism (different chain length), positional isomerism (different position of functional group) and functional group isomerism (different functional groups with the same molecular formula).
What is the difference between a straight-chain and a branched organic molecule?
A straight-chain molecule has all carbon atoms connected in one continuous chain. A branched molecule has one or more side groups attached to the main carbon chain. Both are aliphatic provided they do not contain a benzene ring.
To deduce isomers of C4H10, first draw ........., then consider whether .......... isomerism applies. There are .......... structural isomers of C4H10.
To deduce isomers of C4H10, first draw butane (straight chain), then consider whether chain isomerism applies. There are 2 structural isomers of C4H10.
True or False?
Functional group isomers have very similar chemical properties because they share the same molecular formula.
False.
Functional group isomers have very different chemical properties. Different functional groups lead to different reactivity, even though the molecular formula is identical.
How do you determine whether a molecule is a cyclic compound?
A cyclic compound has its carbon atoms connected in a ring structure. It is still aliphatic as long as it does not contain a benzene ring. Cyclopentane is an example of a cyclic aliphatic compound.
What are stereoisomers?
Stereoisomers are compounds that have the same atoms connected in the same order, but with the atoms arranged differently in space. E/Z isomers are a type of stereoisomerism arising from restricted rotation about a C=C double bond.
True or False?
E/Z isomerism can arise when both carbons of a C=C double bond carry two identical groups.
False.
E/Z isomerism only arises when each carbon of the double bond carries two different groups. If either carbon has two identical groups, the restricted rotation produces no distinct isomers.
In E/Z nomenclature, the .......... isomer has the highest priority groups on the same side of the double bond, while the .......... isomer has them on opposite sides. Priority is assigned using .......... rules based on atomic number.
In E/Z nomenclature, the Z isomer has the highest priority groups on the same side of the double bond, while the E isomer has them on opposite sides. Priority is assigned using Cahn-Ingold-Prelog (CIP) rules based on atomic number.
Explain why the C=C double bond prevents free rotation.
The C=C double bond consists of a sigma bond and a pi bond. The pi bond is formed by sideways overlap of p orbitals above and below the plane of the molecule. Rotation would break this overlap, so rotation is restricted without breaking the pi bond.
When the first atom attached to each C of the C=C is the same, you must look at the .......... atoms attached. The group with the higher .......... on that second atom takes priority.
When the first atom attached to each C of the C=C is the same, you must look at the second atoms attached. The group with the higher atomic number on that second atom takes priority.
True or False?
The terms cis/trans isomerism and E/Z isomerism describe exactly the same set of compounds in all cases.
False.
Cis/trans is a special case of E/Z isomerism that applies when each C of the double bond carries one H. E/Z uses CIP priority rules and applies to a wider range of compounds. AQA requires E/Z nomenclature but also accepts cis/trans where applicable.
What are Cahn-Ingold-Prelog (CIP) priority rules?
Cahn-Ingold-Prelog (CIP) priority rules are a set of rules used to assign priority to groups attached to a C=C bond in E/Z isomerism. The group with the higher atomic number at the point of difference takes priority. Used to determine whether an isomer is E (opposite sides) or Z (same side).
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