SK025 Chemistry Interactive Notes: Physical and Organic Chemistry

Comprehensive vocabulary flashcards reviewing fundamental definitions, laws, named reagents, and reaction mechanisms across Semester 2 Chemistry (SK025).

Reaction Kinetics

The study of the rates of chemical reactions, the factors that influence these rates, and the mechanisms by which the reactions occur.

Reaction Rate

The change in the concentration of a reactant or a product with time, typically expressed in units of $\text{mol}\,\text{L}^{-1}\,\text{s}^{-1}$, $\text{mol}\,\text{dm}^{-3}\,\text{s}^{-1}$, or $\text{M}\,\text{s}^{-1}$.

Differential Rate Equation

An equation that relates the rate of disappearance of reactants to the rate of appearance of products by dividing each rate of concentration change by its stoichiometric coefficient.

Rate Law

An equation that expresses the relationship between the rate of a chemical reaction, the rate constant ($k$), and the concentrations of reactants raised to powers equal to their reaction orders.

Order of Reaction

The power of a reactant's concentration in the rate law that defines how the reaction rate is affected by that specific reactant's concentration.

Half-life ($t_{1/2}$)

The time required for the concentration of a reactant to decrease to half of its initial value.

Activation Energy ($E_a$)

The minimum amount of kinetic energy required by colliding reactant molecules to initiate a chemical reaction.

Activated Complex

An unstable, temporary species formed in the transition state during an effective collision of reactants when the system is at its maximum potential energy.

Catalyst

A substance that provides an alternative reaction pathway with a lower activation energy to increase the rate of a chemical reaction without itself being consumed.

Arrhenius Equation

The mathematical expression $k = A e^{-E_a/RT}$ showing the effect of absolute temperature ($T$) and activation energy ($E_a$) on the rate constant ($k$), where $A$ is the frequency factor and $R$ is the universal gas constant.

Standard Enthalpy of Formation ($\Delta H_f^\circ$)

The heat change when $1\,\text{mole}$ of a compound is formed from its elements in their most stable states at standard temperature ($298\,\text{K}$) and pressure ($1\,\text{atm}$).

Standard Enthalpy of Combustion ($\Delta H_c^\circ$)

The heat released when $1\,\text{mole}$ of a substance is burned completely in excess oxygen at standard temperature ($298\,\text{K}$) and pressure ($1\,\text{atm}$).

Standard Enthalpy of Neutralisation ($\Delta H_n^\circ$)

The heat released when $1\,\text{mole}$ of water ($\text{H}_2\text{O}$) is formed from the neutralisation of an acid and a base at standard temperature ($298\,\text{K}$) and pressure ($1\,\text{atm}$).

Standard Enthalpy of Atomisation ($\Delta H_a^\circ$)

The heat absorbed when $1\,\text{mole}$ of gaseous atoms is formed from its element in its most stable state at standard temperature ($298\,\text{K}$) and pressure ($1\,\text{atm}$).

Specific Heat Capacity ($c$)

The amount of heat required to raise the temperature of one gram of a substance by one degree Celsius ($\text{J}\,\text{g}^{-1}\,^\circ\text{C}^{-1}$).

Heat Capacity ($C$)

The amount of heat required to raise the temperature of a given quantity of a substance by one degree Celsius ($\text{J}\,^\circ\text{C}^{-1}$).

Hess's Law

States that when reactants are converted to products, the total change in enthalpy is the same whether the reaction takes place in one step or in a series of steps.

Lattice Energy of Formation ($\Delta H_{\text{lattice}}$)

The energy released when $1\,\text{mole}$ of a solid ionic compound is formed from its constituent gaseous ions.

Electron Affinity (EA)

The heat change when an electron is added to $1\,\text{mole}$ of gaseous atoms or ions in their ground state.

Born-Haber Cycle

An energy cycle approach based on Hess's Law used to analyse reaction energies and calculate the lattice energy of ionic compounds from accessible experimental values.

Standard Reduction Potential ($E^\circ$)

A quantitative measure of the tendency of a chemical species to attract electrons and undergo reduction at standard state conditions ($25\,^\circ\text{C}$, $1.0\,\text{M}$, and $1.0\,\text{atm}$).

Standard Hydrogen Electrode (SHE)

A reference electrode consisting of a platinum electrode immersed in $1.0\,\text{M}\,\text{H}^+$ solution and bubbled with hydrogen gas at $1\,\text{atm}$ and $25\,^\circ\text{C}$, with an assigned reduction potential of $0.00\,\text{V}$.

Nernst Equation

An equation relating non-standard cell potential ($E_{\text{cell}}$) to standard cell potential ($E^\circ_{\text{cell}}$), temperature, electron moles transferred ($n$), and reaction quotient ($Q$): $E_{\text{cell}} = E^\circ_{\text{cell}} - \frac{0.0592}{n}\log Q$ at $298.15\,\text{K}$.

Faraday's First Law of Electrolysis

States that the quantity or mass of a substance formed or discharged at an electrode is directly proportional to the quantity of electric charge ($Q$) supplied ($m \propto Q$).

Homologous Series

A family of organic compounds sharing the same functional group and similar chemical properties, in which each successive member differs by a constant $-\text{CH}_2-$ unit.

Functional Group

An atom or group of atoms within an organic molecule that determines its characteristic chemical properties and reaction types.

Constitutional Isomers

Different compounds possessing the same molecular formula but differing in the connectivity or order of attachment of their atoms.

Chirality Centre

An $\text{sp}^3$-hybridised carbon atom that is bonded to four completely different atoms or groups.

Enantiomers

A pair of stereoisomers that are non-superimposable mirror images of each other and rotate plane-polarized light in equal magnitudes but opposite directions.

Homolytic Cleavage

The symmetrical breaking of a non-polar covalent bond where each bonded atom retains one electron, resulting in the formation of two free radicals.

Heterolytic Cleavage

The unsymmetrical breaking of a polar covalent bond where both bonding electrons are transferred to the more electronegative atom, producing a cation and an anion.

Electrophile

An electron-deficient species (either neutral or positively charged) that acts as a Lewis acid by accepting an electron pair from a nucleophile.

Nucleophile

An electron-rich species (either neutral or negatively charged) that acts as a Lewis base by donating a pair of electrons to an electron-deficient centre.

Saytzeff's Rule

A rule stating that in an elimination reaction, the alkene containing the more highly substituted double bond (greater number of alkyl substituents) is the major and more stable product.

Markovnikov's Rule

A rule stating that in the electrophilic addition of an unsymmetrical reagent to an alkene, the electrophile (usually hydrogen) adds to the double-bonded carbon atom bonded to the greater number of hydrogen atoms.

Anti-Markovnikov Addition

The addition of $\text{HBr}$ to an alkene in the presence of peroxides ($\text{ROOR}$ or $\text{H}_2\text{O}_2$) where hydrogen attaches to the double-bonded carbon having fewer hydrogen atoms.

Addition Polymerisation

A reaction in which unsaturated alkene monomers repeatedly join together by breaking their $\pi$ bonds to form a long chain polymer without the elimination of any small molecule.

Hückel's Rule

A rule stating that a planar, cyclic, and completely conjugated system exhibiting enhanced aromatic stability must contain $(4n + 2)$ $\pi$ electrons, where $n$ is a non-negative integer ($0, 1, 2, \dots$).

Electrophilic Aromatic Substitution

A characteristic reaction of benzene and its derivatives where an electrophile replaces a hydrogen atom on the aromatic ring while preserving the stable delocalised $\pi$-electron system.

SN1 Mechanism

A two-step unimolecular nucleophilic substitution process where the rate-determining step involves only the haloalkane forming a carbocation intermediate before attack by a weak nucleophile.

SN2 Mechanism

A concerted, one-step bimolecular nucleophilic substitution process involving backside attack by a strong nucleophile on the electrophilic carbon and simultaneous departure of the leaving group via a single transition state.

Grignard Reagent

An organomagnesium halide ($\text{RMgX}$ or $\text{ArMgX}$) synthesised by reacting a haloalkane with magnesium metal in anhydrous ether, widely used in carbon-carbon bond forming reactions.

Lucas Reagent

A mixture of concentrated hydrochloric acid ($\text{HCl}$) and anhydrous zinc chloride ($\text{ZnCl}_2$) used to classify alcohols as primary, secondary, or tertiary based on the rate of turbidity formation.

Iodoform Test

A qualitative test using iodine in aqueous sodium hydroxide ($\text{I}_2 / \text{NaOH}$) to detect methyl carbinol ($\text{CH}_3\text{CH(OH)}-$) or methyl carbonyl ($\text{CH}_3\text{C}=\text{O}$) groups through the formation of a yellow triiodomethane ($\text{CHI}_3$) precipitate.

Phenol

An aromatic hydroxy compound where a hydroxyl group ($-\text{OH}$) is bonded directly to a benzene ring, behaving as a stronger acid than aliphatic alcohols due to resonance stabilisation of the phenoxide ion.

Brady's Reagent

A solution of 2,4-dinitrophenylhydrazine (2,4-DNPH) in acidic medium used to identify the presence of a carbonyl group ($\text{C}=\text{O}$) in aldehydes and ketones by yielding an orange or yellow precipitate.

Tollens' Reagent

An ammoniacal silver nitrate solution ($[\text{Ag}(\text{NH}_3)_2]^+, \, ^-\text{OH}$) that oxidises aldehydes to carboxylate ions while depositing metallic silver as a reflective silver mirror on the reaction vessel.

Fehling's Reagent

An alkaline solution containing copper(II) sulfate complexed with tartrate ions used to distinguish aliphatic aldehydes (which yield a brick-red $\text{Cu}_2\text{O}$ precipitate) from aromatic aldehydes and ketones.

Fischer Esterification

An acid-catalyzed condensation reaction between a carboxylic acid and an alcohol under reflux to produce an ester and water.

Condensation Polymerisation

A polymerisation process where bifunctional or polyfunctional monomers combine with the continuous elimination of small molecules such as $\text{H}_2\text{O}$, $\text{HCl}$, or $\text{CH}_3\text{OH}$.

Hinsberg's Test

A chemical test employing benzenesulphonyl chloride in excess aqueous base followed by acidification to differentiate primary, secondary, and tertiary amines.

Nitrous Acid Test

A qualitative test using freshly prepared cold nitrous acid ($\text{NaNO}_2 + \text{HCl}$ at $0\text{--}5\,^\circ\text{C}$) that distinguishes primary, secondary, and tertiary amines based on observations like effervescence, yellow oils, or diazonium formation.

Hoffmann's Degradation

A reaction in which a primary amide is warmed with bromine in aqueous sodium hydroxide ($\text{Br}_2 / \text{NaOH}$) to produce a primary amine having one fewer carbon atom than the starting amide.

Zwitterion

An internal dipolar ion carrying separate positive and negative charges on different atoms within the same molecule, resulting in an overall electrical charge of zero.

Isoelectric Point ($pI$)

The specific $\text{pH}$ at which an amino acid carries no net electrical charge and its dipolar zwitterion form reaches maximum concentration.

Peptide Bond

An amide covalent linkage ($-\text{CO}-\text{NH}-$) formed between the carboxyl group of one amino acid and the amino group of another with the elimination of a water molecule.