GRADE 12 REVISION 2013 MATTER AND MATERIALS: ORGANIC MOLECULES TERMS AND DEFINITIONS

GRADE 12 REVISION 2013: MATTER AND MATERIALS - ORGANIC MOLECULES TERMS AND DEFINITIONS

Organic Chemistry

Definition: The chemistry of carbon compounds.

Homologous Series

Definition: A group of organic compounds that can be described by the same general formula and possess the same functional group.
Characteristics: Each member differs from the next by a CH₂ group.

General Formula

Definition: A formula used to determine the molecular formula of any member in a homologous series.
Example: Alkanes have the general formula $CnH{2n+2}$ .
Specific example: The alkane with 100 carbon atoms is $C{100}H{202}$ .

Functional Group

Definition: A bond, atom, or group of atoms that determine the physical and chemical properties of a group of organic compounds.

Molecular Formula

Definition: A chemical formula that indicates the type of atoms and the precise number of each in a molecule.
Example: For propane, the molecular formula is $C3H8$ .

Condensed Structural Formula

Definition: A representation showing how atoms are bonded together in a molecule without all bond lines.
Example: For propane, it can be written as $CH3CH2CH_3$ .

Structural Formula

Definition: A detailed representation showing atoms and their bonds in a molecule; lines used depict all bonding interactions.
Note: Do not depict actual geometry/shape.

Isomerism

Definition: The property of an organic molecule to have a molecular formula that corresponds to that of another molecule.
Structural Isomers: Compounds with the same molecular formula but different structural formulae.

Hydrocarbons

Definition: Compounds that consist of carbon (C) and hydrogen (H) atoms only.

Substituent

Definition: A group or branch attached to the longest continuous chain of carbon atoms in an organic compound.

Alkanes

Description: Organic compounds containing only C-H and C-C single bonds.
General formula: $CnH{2n+2}$ .
Type: Saturated hydrocarbons (maximum hydrogen per carbon, no double or triple bonds).

Unsaturated Hydrocarbons

Definition: Hydrocarbons with carbon-carbon double bonds that do not contain the maximum number of hydrogen atoms.

Alkyl Group

Definition: A group formed by removing one hydrogen atom from an alkane.

Cycloalkanes

Definition: Organic compounds of carbon and hydrogen where carbon atoms are bonded in rings with single bonds only.
General formula: $CnH{2n}$ .

Alkenes

Definition: Compounds of carbon and hydrogen containing at least one carbon-carbon double bond.
General formula: $CnH{2n}$ .

Cycloalkenes

Definition: Compounds of carbon and hydrogen in which carbon atoms are bonded in a ring containing one double bond.
General formula: $CnH{2n-2}$ .

PAGE 2 TERMS AND DEFINITIONS

Diene

Definition: A compound of carbon and hydrogen that contains two carbon-carbon double bonds.
General formula: $CnH{2n-2}$ .

Alkyne

Definition: A compound of carbon and hydrogen that contains a carbon-carbon triple bond.
General formula: $CnH{2n-2}$ .

Haloalkane (Alkyl Halide)

Definition: An organic compound in which one or more hydrogen atoms in an alkane have been replaced with halogen atoms.
General formula: $CnH{2n+1}X$ where $X$ can be F, Cl, Br, or I.

Primary Haloalkane

Definition: One carbon atom is bonded to the carbon that is bonded to the halogen.
Example: Ethyl bromide $C2H5Br$ .

Secondary Haloalkane

Definition: Two carbon atoms bond to the carbon that's bonded to the halogen.

Tertiary Haloalkane

Definition: Three carbon atoms bond to the carbon that is bonded to the halogen.

Alcohol

Definition: An organic compound where hydrogen atoms in an alkane have been replaced with hydroxyl groups (-OH).
General formula: $CnH{2n+1}OH$ .

Primary Alcohol

Definition: One carbon atom is bonded to the carbon bonded to the hydroxyl group.

Secondary Alcohol

Definition: Two carbon atoms are bonded to the carbon that is bonded to the hydroxyl group.

Tertiary Alcohol

Definition: Three carbon atoms are bonded to the carbon that is bonded to the hydroxyl group.

PAGE 3 TERMS AND DEFINITIONS

Aldehydes

Definition: Organic compounds having the general structure $RCHO$ where R = H or an alkyl group.
General formula: $RCHO$ .

Carboxyl Group

Definition: The functional group of carboxylic acids (-COOH).

Carbonyl Group

Definition: The functional group of ketones (>C=O).

Boiling Point

Definition: The temperature at which the vapor pressure of a liquid equals external atmospheric pressure.

Melting Point

Definition: The temperature at which a solid transitions to a liquid phase.

Viscosity

Definition: The resistance of a fluid (liquid or gas) to flow; higher viscosity results in slower flow.

Vapor Pressure

Definition: The pressure at which the vapor of a substance is in dynamic equilibrium with its liquid or solid form.
Note: Substances with high vapor pressure are volatile with high volatility.

Organic Reactions

Substitution Reaction: Reaction where an atom or group in a molecule is replaced by another atom or group.
Elimination Reaction: Reaction where elements from the starting material are lost, forming a double bond.
Addition Reaction: Reaction where a double bond in the starting material is broken and new elements are added.
Halogenation: Reaction of a compound with a halogen (Br₂, Cl₂, I₂, F₂).
Cracking: The process of breaking down molecules with large molecular mass into smaller molecules.
Hydrogenation: The addition of hydrogen to a molecule.
Hydrohalogenation: The addition of a hydrogen halide (HX) to a molecule.
Hydration: The addition of water to a molecule.
Dehydrohalogenation: Elimination reaction where hydrogen and a halogen are removed from a molecule.
Dehydration: Removal of water from a molecule.
Esterification: The reaction of a carboxylic acid with an alcohol to form an ester.

FUNCTIONAL GROUPS OF ORGANIC COMPOUNDS

Homologous series	Structure of functional group	Example of a compound
Alkanes	Only single bonds (C-H, C-C)	Ethane
Alkenes	Double bonds	Ethene
Alkynes	Triple bonds	Ethyne
Haloalkanes (alkyl halides)	X = F, Cl, Br, I	Bromoethane
Alcohols (alkanols)	-OH group	Ethanol
Aldehydes	RCHO	Ethanal
Ketones	>C=O	Propan-2-one
Carboxylic acids	-COOH	Ethanoic acid
Esters	RCOOR'	Methyl ethanoate

NAMING OF ORGANIC COMPOUNDS

Structure: The name of organic molecules consists of three parts:
- Parent Name: Indicates the number of carbon atoms in the longest chain of the molecule.
- Suffix: Indicates the functional group present.
- Prefix: Reveals the identity, location, and number of substituents attached to the carbon chain.

Number of Carbon Atoms	Parent Name
1	meth
2	eth
3	prop
4	but
5	pent
6	hex
7	hept
8	oct

PHYSICAL PROPERTIES OF ORGANIC COMPOUNDS

Relationships

Vapor Pressure vs. Boiling Point:
- High boiling points correlate with low vapor pressures.
Physical Properties and Intermolecular Forces:
- The strength of intermolecular forces directly impacts physical properties:
- Stronger intermolecular forces lead to higher boiling points, melting points, viscosities and lower vapor pressures.

Types of Intermolecular Forces

Strong Hydrogen Bonds:
- Present in molecules where H is covalently bonded to N, O, or F (e.g., Alcohols and Carboxylic Acids).
Weak Van der Waals Forces (London Dispersion Forces):
- Present in all molecules, stronger in polar molecules compared to non-polar ones.

Relationships Influencing Properties

Chain Length:
- Increasing length enhances surface area and intermolecular force strength, leading to increased boiling point/melting point/viscosity but decreased vapor pressure.
Branching:
- Increased branching decreases surface area and intermolecular forces, lowering boiling points while increasing vapor pressure.
Polarity of Functional Groups:
- Increasing polarity increases intermolecular force strength, raising boiling/melting points and viscosity but lowering vapor pressure.

SUMMARY OF ORGANIC REACTIONS GRADE 12

Reactions of Alkenes

Hydrogenation:
- Conditions: Catalyst (Pt, Pd, or Ni)
- Reactants: Alkene + H₂
- Product: Alkane
Halogenation:
- Conditions: Unreactive solvent
- Reactants: Alkene + X₂ (X = Cl, Br)
- Product: Haloalkane
Hydrohalogenation:
- Conditions: No water; unreactive solvent
- Reactants: Alkene + HX (X = I, Br, Cl)
- Major product: An H atom bonds to the C with more H atoms.
Hydration:
- Conditions: Excess H₂O; small amount of acid (H₂SO₄ or H₃PO₄) as catalyst.
- Reactants: Alkene + H₂O
- Product: Alcohol(s)

Addition Reactions

Include various types (listed under Additions above).

Elimination Reactions of Alkanes

Oxidation (Combustion):
- General form: Alkane + Oxygen -> Carbon Dioxide + Water + Energy
Substitution Reaction:
- Alkane + Halogen -> Haloalkane + HX

STRUCTURED QUESTIONS PRACTICAL EXAMPLES

Utilize the names and types of reactions described throughout to develop practical exercises, for example, balancing equations, predicting products based on reaction conditions, and utilizing structural formulas for representations in structured questions.

CASE STUDIES AND REAL-WORLD APPLICATIONS

Include implications of organic chemistry in pharmaceuticals (using alcohols and esters), environmental impacts of organic compound use (petrol vs. alcohols), and technological needs for fuels as sustainable resources, such as alcohols and fossile fuel alternatives.

Maintain a detailed approach integrating practical insights, ethical considerations, and contextual understanding into organic molecules and reactions to enhance learning outcomes for Grade 12 students.