oundCONTENT STANDARD 2.2 : HOMOLOGOUS SERIES
LEARNING STANDARD 2.2.1 : EXPLAIN HOMOLOGOUS SERIES1. Is a series of classification of organic chemicals that havethesamefunctional group 2. The functional group determines the chemical propertiesofthehomologous series. 3. Chemical reactions occur at the functional group. 4. The homologous series that we will learn in this chapterare alkane, alkene, alkyne, alcohol, carboxylic acid andester
5. Characteristics of the homologous series: Ø each member in same homologous series has same general formula.Ø each member in same homologous series same functional group,sothey have same chemical properties Ø each member in the homologous series differs from the following member by one carbon atom and two hydrogen atoms(CH2or,relative molecular mass = 14). Ø Members of the series shows gradually change in physical properties (down the homologous series) Ø member of a homologous series can be prepared by same method
LEARNING STANDARD 2.2.2 : CONSTRUCT MOLECULAR FORMULAE AND STRUCTURAL FORMULA AND NAME THE MEMBERS OF THE HOMOLOGOUS SERIES 1. Molecular formula : chemical formula that shows theactualnumberof atoms of each element in a molecule /compounds2. Structural formula : formula that shows howthe atomsinamoleculeor compounds are bonded to each other
3. The names of the members of each homologous series, accordingtothe IUPAC nomenclature consist of two components whichare: Ø the root name shows the number of carbon atomsinthelongestcontinuous carbon chain Ø the suffix shows the homologous series of members
Example: First member, n = 1 Molecular formula: C1 H2(1) + 2 = CH4 Name of member: Methane
Example: First member, n = 2 Molecular formula: C2H2(2) = C2H4 • Root name: Obtained from the longest carbon chain. • Add the suffix “ene” to the root name because “ene” is a member of the alkene homologous series. Name of member: Ethene
Example: First member, n = 2 Molecular formula: C2H2(2)−2 = C2H2 • Root name: Obtained from the longest carbon chain. • Add the suffix “yne” to the root name because “yne” is a member of the alkyne homologous series. Name of member: Ethyne
Example: Third member, n = 3 Molecular formula: C3H2(3)+1OH = C3H7OH •Naming of straight chain alcohols according to the IUPAC nomenclature: (i) Determine the number of carbon atoms in the longest continuous carbon chain containing the hydroxyl group OH (ii) Numbering starts from the carbon atom that is nearest to the hydroxyl group at the end of chain (iii) Replace the “e” ending from the alkane name with “ol”. Propan-1-ol
Ant bites that cause pain contain methanoic acid, HCOOH or formic acid. Vinegar contains ethanoic acid, CH3COOH, which is also known as acetic acid. Example: First member, n = 0 Molecular formula: C0 H2(0) +1COOH = HCOOH Name : methanoic acid
•Naming of carboxylic acids according to the IUPAC nomenclature: (i) Determine the number of carbon atoms, and state thecorrespondingalkane name. (ii) Replace the “e” ending from the alkane name with “oic acid”. Example: (a) Molecular formula: HCOOH The number of carbon atom is 1 The corresponding alkane name is methane. The name for HCOOH is methanoic acid (b) Molecular formula: CH3COOH The number of carbon atoms is 2 The corresponding alkane name is ethane. The name for CH3COOH is ethanoic acid
LEARNING STANDARD 2.2.3: PHYSICAL PROPERTIES OF COMPOUNDS IN A HOMOLOGOUS SERIES Physical Properties of Alkanes, Alkenes and AlkynesPhysical properties Reasons(a) Insoluble in water and soluble in organic solvent Consists of neutral moleculeonly(b) Cannot conduct electricity in any state (c) Melting and boiling point lower molercules are attractedbyweakintermolecular forces1. Physical properties generally:
2. As the number of carbon atoms per molecule increases: Ø molecular size increases, Ø the Van der Waals force or the attraction betweenmoleculesbecomes stronger. Ø More heat energy is needed to overcome this forceØ therefore the melting point and boiling point alsoincrease.
QUIZ Why melting and boiling point of propane is higher thanethane?(a) .................... have more number of carbon atoms per moleculethan .................. (b) Size of ...................... molecule is bigger than ................. (c) Force of attraction between the molecules become....................(d) More ........................is needed to ........................ the forces
Physical Properties of Alcohol and Carboxylic acid 1. Alcohols and carboxylic acids are non hydrocarbonorganiccompounds containing carbon, hydrogen and oxygen. 2. The boiling points of alcohols and carboxylic acidsarerelativelyhigher than their corresponding alkenes. 3. Their solubility in water decreases as the moleculesizeincreases.
4. Physical properties of alcohol: TERMS OF PROPERTIES(a) State Alcohol (C1 - C11) are liquid at roomtemperature(b) Solubility Simple alcohol (methanol, ethanol, propanol)arevery soluble in water (c) Colour Colourless (d) Odour Sharp smell and dissoles in water. Veryvolatile(e) Flame Burnt with a blue flame
5. Physical properties of carboxylic acid: (a) Colourless liquid (b) Pure (glacial) ethanoic acid does not contain water -existsasneutralmolecule (c) sharp or pungent smell like vinegar (d) boiling point increases as number of carbon atomspermoleculesincreases (e) very soluble in water (methanoic acid, ethanoic acid&propanoicacid(f) can conduct electricity when water is present becausehasfreelymoving ions.