Chapter 13 – Foundations of Organic Chemistry

A comprehensive set of flashcards covering key concepts from Chapter 13: properties of organic compounds, formulae types, functional groups, IUPAC naming rules and priorities, bonding and hybridisation, structural and stereoisomerism, reaction mechanisms (homolytic/heterolytic), and the principal classes of organic reactions.

What type of bonding predominates in organic compounds?

Mostly covalent bonding.

State two typical physical properties of organic compounds compared with inorganic compounds.

They usually have low melting points and are mostly insoluble in water.

How many different organic compounds are known or synthesised approximately?

About 4 million.

Give two carbon-containing substances classified as inorganic, even though they contain carbon.

Carbon monoxide (CO) and carbon dioxide (CO₂).

Define ‘empirical formula’.

The simplest whole-number ratio of atoms in a molecule.

Define ‘molecular formula’.

The actual number of each type of atom in one molecule.

What information does a structural formula convey?

How each atom is bonded to every other in the molecule.

Which formula shows every bond explicitly in 2-D form?

Displayed formula.

Which simplified formula omits C and H symbols, showing only bonds between non-hydrogen atoms?

Skeletal formula.

What does a wedge bond represent in a 3-D displayed formula?

A bond coming out of the plane of the paper toward the viewer.

Give the general definition of a functional group.

A specific atom or group of atoms that confers characteristic chemical properties on an organic molecule.

What is a homologous series?

A family of molecules with the same functional group in which successive members differ by –CH₂–.

How does increasing carbon-chain length affect boiling point?

Boiling point increases due to stronger van der Waals forces.

Name the three major categories of hydrocarbons.

Alkanes, alkenes and alkynes.

List two oxygen-containing functional-group families.

Alcohols and carbonyl compounds (aldehydes/ketones).

What is the first step in IUPAC naming of an organic molecule?

Identify the longest continuous carbon chain (the parent chain).

When multiple different substituents are present, in what order are they listed?

Alphabetical order, each with its lowest possible locant number.

Which Greek prefixes are used for multiple identical substituents?

di-, tri-, tetra-, penta-, etc.

What punctuation separates numbers from letters in an IUPAC name?

A hyphen (dash).

Give the highest-priority functional group among the following: alcohol, carboxylic acid, ketone.

Carboxylic acid.

What suffix is used for an aldehyde in IUPAC nomenclature?

-al

State the priority order of the first four functional groups in IUPAC naming.

1 Carboxylic acid > 2 Ester > 3 Nitrile > 4 Aldehyde.

What prefix is used for a halogen substituent?

Fluoro-, chloro-, bromo- or iodo- as appropriate.

How many covalent bonds can carbon form maximally?

Four covalent bonds.

What is catenation?

The ability of carbon atoms to form long chains with other carbon atoms.

What is the bond angle around an sp³-hybridised carbon?

Approximately 109.5° (tetrahedral).

Give the geometry and bond angle of an sp²-hybridised carbon.

Trigonal planar, 120°.

Which hybridisation corresponds to a linear geometry?

sp hybridisation, bond angle 180°.

Define structural isomerism.

Compounds with the same molecular formula but different structural formulae.

What distinguishes chain isomers?

Different carbon skeleton (straight vs. branched) but same functional group.

What is a positional isomer?

Same skeleton and functional group but the functional group occupies different positions.

Define functional-group isomerism.

Same molecular formula but different functional groups present.

What prevents free rotation in alkenes, leading to geometric isomers?

The presence of a π-bond in the C=C double bond.

In cis-trans isomerism, where are higher-priority groups located in the cis isomer?

On the same side of the double bond or ring.

What is a chiral (asymmetric) carbon?

A carbon atom bonded to four different atoms/groups.

How many optical isomers exist for a molecule with n chiral centres?

2ⁿ possible stereoisomers.

What is a racemic mixture?

A 1:1 mixture of two enantiomers that is optically inactive overall.

Distinguish dextrorotatory and levorotatory isomers.

Dextrorotatory (d or +) rotates plane-polarised light clockwise; levorotatory (l or –) rotates it anticlockwise by the same angle.

Define homolytic fission.

Bond breaking in which each atom retains one electron, forming free radicals.

What type of reactive species is produced in homolytic fission?

A free radical with an unpaired electron.

Define heterolytic fission.

Bond breaking where both bonding electrons go to the more electronegative atom, forming an ion pair.

Name the cation produced when a carbon atom becomes electron-deficient in heterolysis.

Carbocation.

What is a carbanion?

A negatively charged carbon species bearing a lone pair of electrons.

Define electrophile.

A species that accepts an electron pair to form a new bond.

Define nucleophile.

A species that donates an electron pair to form a new bond.

What characterises an addition reaction in organic chemistry?

Two or more reactants combine to form a single product.

Describe an elimination reaction.

Removal of a small molecule from a larger one, generating multiple bonds.

What occurs in a substitution reaction?

One atom or group in a molecule is replaced by another atom or group.

Define hydrolysis.

Breaking a bond using water, which provides H and OH fragments.

What small molecules are commonly lost during condensation reactions?

Water (H₂O) or hydrogen chloride (HCl).

How is oxidation viewed in organic reactions?

Addition of oxygen or removal of hydrogen (symbolised by [O]).

Conversely, how is reduction viewed in organic chemistry?

Addition of hydrogen or removal of oxygen (symbolised by [H]).

Which reaction mechanism illustrates electrophilic addition to alkenes?

Bromine addition to propene forming 1,2-dibromopropane via a bromonium ion intermediate.

When numbering a chain containing both a double bond and an alcohol group, which gets the lowest locant if alcohol has higher priority?

The carbon bearing the OH group receives the lowest possible number.

What suffix is used for nitriles?

-nitrile

What is the prefix for an alkoxy substituent?

-alkoxy (e.g., methoxy-).

Give an example of an isoalkyl group.

Isopropyl (1-methylethyl).

What does ‘VDW forces’ stand for, and why are they important in organic molecules?

Van der Waals forces; they influence melting and boiling points as chain length changes.

What structural feature allows cis-trans isomerism in cyclic compounds?

Restricted rotation about C–C single bonds within the ring framework.

Why do optical isomers often show identical chemical reactivity toward achiral reagents?

Because achiral environments do not differentiate between mirror-image structures.

Which type of isomerism involves free rotation about single bonds giving rise to rotamers?

Conformational isomerism (a subset of stereoisomerism).

What hybridisation change occurs when carbon is promoted from ground to excited state before bonding?

An electron moves from 2s to 2p, enabling sp, sp² or sp³ hybridisation.

What term describes the breaking and making of bonds step-by-step in an organic reaction?

Reaction mechanism.

Which type of covalent bond fission typically initiates free-radical chain reactions in halogenation of alkanes?

Homolytic fission of the halogen molecule (e.g., Cl₂ → 2 Cl•).

During heterolytic fission of C–X (X = halogen), which product obtains the negative charge?

The halogen atom (X⁻) because it is more electronegative.

Name two reaction conditions that often promote elimination from alcohols.

Heating with concentrated sulfuric acid or alumina catalyst.

Which functional group uses the suffix ‘-one’?

Ketone.

Give the IUPAC name for CH₃CH₂OH.

Ethanol (or systematically, ethyl alcohol).

What is the parent chain length indicated by the stem ‘pent-’?

Five carbon atoms.

What is the point of commas in an IUPAC name?

To separate multiple locant numbers (e.g., 2,3-dimethyl).

Why do branched isomers of the same molecular formula usually have lower boiling points than straight-chain isomers?

Branching lowers surface area, reducing van der Waals attractions.