3RD TERM

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TOPIC: ORGANIC CHEMISTRY
BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
a. Explain alkyl group ad functional group.
b. List the common homologous series and their general molecular formulae.
c. Define esterification.
REFERENCE: NEW SCHOOL CHEMISTRY FOR SSS by OSEI YAW ABABIO (New Edition)

CONTENTS: ALKYL GROUPS AND FUNCTIONAL GROUPS
ALKYL GROUPS: is the group derived from the alkane by the loss of a hydrogen atom. Alkyl groups have the general formula of CnH2n+1 (and are given the general symbol R). The names end with -yl e.g CH3-(methyl); C2H5-(ethyl); C3H7- (propyl); C4H9 -(butyl); C5H11-(pentyl); C6H13- (hexyl).

FUNCTIONAL GROUP is an atom, a radical (group of atoms) or a bond common to a homologous series, and which determines the main chemical properties of the series, e.g. _ COOH (carboxylic acid); -COOR (alkanoate).
Note: Alkyl groups contribute to mass and physical properties while the functional group is responsible for chemical properties of the compound.

COMMON HOMOLOGOUS SERIES
1. ALKANES: CnH2n+2 ; the names end with -ane, e.g. methane (CH4), ethane (C2H6) and propane (C3H8).

2. ALKENES: CnH2n; the names end with -ene, e.g. ethane (C2H4), propene (C3H6), and butane (C4H8).

3. ALKYNES: triple bond hydrocarbons, CnH2n-2; the names end with -yne e.g. ethyne (C2H2), propyne (C3H4), butyne (C4H6) and pentyne (C5H8).

4. ALKANOLS (ALCOHOLS): R-OH; the names end with -ol after the corresponding alkane, e.g. CH3OH (methanol), C2H5OH (ethanol), C3H7OH (propanol).
5. ALKANOIC ACID (CARBOXYLIC ACID: they are organic acids, RCOOH and the names end with -oic acid, e.g. ethanoic acid (2CH31COOH), methanoic acid H1COOH), propanoic acid (3CH32CH21COOH) and butanoic acid (4CH33CH22CH21COOH).

6. ESTERS (ALKANOATES): esters, RCOOR1, are formed when a carboxylic acid reacts with an alkanol, a process called ESTERIFICATION.

ESTERIFICATION is the reaction in which an alkanoic acid (carboxylic acid or organic acid) reacts with an alkanol (alcohol or organic alkali) to form alkanoate (ester or organic salt) and water only e.g.
RCOOH + R1OH RCOOR1 + H20.
In naming an ester, the alkyl group R1is named first, followed by the name of the acid group with -oate ending. For example, HCOOCH3 is methylmethanoate and CH3(CH2)2COOC2H5 ethylbutanoate, while CH3COOCH3 is methylethanoate.

EVALUATION:
a. Give the general formula of the alkyl group.
b. What is the effect of alkyl group in a homologous series?
c. With the aid of examples, explain functional group and its effect in a homologous series.
d. List six homologous series with the general molecular formula of each.

ASSIGNMENT:
1. Define esterification.
2. Give the difference between esterification and neutralization.






BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
a. List the remaining functional groups (alkanones, alkanols, amines, amides and others).
b. Explain the basic rules for naming organic compound i.e. IUPAC nomenclature for naming organic compounds.

CONTENT: COMMON HOMOLOGOUS SERIES
7. ALKANONES OR KETONES (RCOR1): Their names end with -one, e.g. CH3COCH3 (propan-2-one); CH3COC2H5 (butan-2-one); C4H9COCH3(hexan-2-one).

8. ALKANAL OR ALDEHYDES (RCHO): Their names end with -al, e.g HCHO (methanol); CH3CHO(ethanol); C4H9CHO (pentanal).

9. AMINES (RNH2): are named by adding the -amine ending to the alkyl group e.g CH3NH2 (methylamine); C2H5NH2 (ethylamine); C5H11NH2 (pentylamine).

10. AMIDES (RCONH2): Their names end with -amide e.g. CH3CONH2 is ethanamide; C2H5CH2CONH2 (butanamide); HCONH2 is methanamide.

11. ETHERS (R-O-R1): The prefix -alkoxy is used followed by the name of the corresponding alkane of the other alkyl group in the molecule, (the simple alkyl group is named first with the -yl ending replaced by -oxy). For example, CH3OC2H5 (methoxyethane); C2H50C2H5 (ethoxyethane); C4H9OC3H7 (propoxybutane).

BASIC RULES FOR NAMING ORGANIC COMPOUNDS (IUPAC NOMENCLATURE FOR NAMING ORGANIC COMPOUNDS).
Aliphatic organic compounds can be named by following the basic rules below:
1. Largest continuous carbon chain is taken as the root hydrocarbon and named according to the number of carbon atoms it contains, adding the appropriate suffix to indicate the principal substituent group.

2. The carbon atoms in the root hydrocarbon are numbered from the end which will give the lowest number to the suffix and the prefix (es).

3. Indicate the other substituent by prefixes preceded by numbers to show their positions on the carbon chain.
Correct numbering incorrect numbering
4CH3 - 3CH2 - 2CH - 1CH3 1CH3 - 2CH2 - 3CH - 4CH3
CH3 CH3
2-methylbutane 3-methylbutane

4CH3 - 3 CH2 - 2CH 1CH 4CH3 - 2CH2 - 3CH 4CH
But-1-yne (butyne) but-3-yne

CL3CH2 - 2CH2 - 1CH2OH CL1CH2 - 2CH2 - 3CH2OH
3-chloropropan-1-ol 1- chloropropan-3-ol

EVALUATION:
Name the organic compounds using IUPAC nomenclature.

ASSIGNMENT:
1. Name the compounds C3H7CONH2 and C3H7NH2. Give the correct names of the following compounds:
2. CH3 CH2 CH CH CH3
CH3 CH3
3. CH3 CH CH C CH3
C2H5 CH3
4. CLCH2 CH CH2OH
Br
5. CH3
CH3 C CH3
CH3






BEHAVIOURAL OBJECTIVES: BY THE END OF THE LESSON, THE STUDENTS SHOULD BE ABLE TO:
a. Define stereochemistry.
b. Define isomerism and explain positional isomerism and functional group isomerism.

CONTENTS: STEREOCHEMISTRY (ISOMERISM)
STEREOCHEMISTRY is the study of structure in three dimensions. Isomerism is a stereochemical phenomenon.

ISOMERISM is the existence of two or more compounds (known as isomers) with the same molecular formula but different molecular structures.

1. POSITIONAL ISOMERISM: is one in which isomers with the same molecular formula and belonging to the same homologous series tend to have similar chemical properties (as they have the same functional group), but slightly different physical properties as a result of their structural differences.
H H H H H H H H H
H C C C C C H H C C C C H
H H H H H H H
Pentane (normal pentane) H C H
H
2-methylbutane( iso-pentane)


H
H C H
H H
H C C C H C5H12
H H 2,2-dimethylpropane (iso-pentane)
H C H
H


H H H H H H H
H C C C C H H C C C H
H H H H H H
butane (n-butane) H C H
H
2-methylpropane
(iso-butane)

2. FUNCTIONAL GROUP ISOMERISM: This involves isomers with the same molecular formula but belonging to different homologous series, thus, the isomers have different physical and chemical properties because of their different structural formula and functional groups respectively e.g. ethanol (C2H5OH) is an alkanol while methoxymethane (CH3OCH3) is an ether but both ethanol and methoxymethane have the same molecula fomula of C2H6O.

H H H H
H C C O H H C O C H
H H H H
C2H60 CH3OCH3
Ethanol C2H5OH methoxymethane

EVALUATION:
a. Define isomerism.
b. Give the differences between positional isomerism and functional group isomerism.

ASSIGNMENT:
a. Write four isomers of hexane, C6H14 with the structural formula.
b. Name the compound
Cl Cl
H C C Cl
H2C CH2






BEHAVIOURAL OBJECTIVES: At the end of the lesson, the students should be able to:
1. Explain geometric isomerism with the aid of structural formula.
2. Explain optical isomerism with the aid of structural formulae.

CONTENT: GEOMETRIC ISOMERISM

CH3 CH3 CH3 H
C = C and C = C
H H H CH3
Cis-but-2-ene trans-but-2-ene
In but-2-ene, the presence of double bond between the carbon atoms hinders free rotation. So, the two forms, cis- and trans- are locked in shape giving rise to geometric isomerism. Geometric isomers have similar chemical properties but their physical properties are different, e.g. the trans- form of 1,2-dichloroethene boils at 480C while the cis- form boils at 600C.

H Cl Cl Cl
C = C and C = C
Cl H H H
Trans -1,2-dichloroethene cis-1,2-dichloroethene
Geometric isomerism is common among alkenes. An alkene where each carbon atom joined by a double bond is attached to two different atoms or groups can exist in the cis- and trans- forms.
Note: When two heavy or large groups (groups with large molecular masses) are on the same side of a double bond, the molecule is said to have a cis configuration. When two such groups lie on the opposite side of the double bond (and adjacent), the molecule is said to possess a trans configuration.

OPTICAL ISOMERISM: is the existence of two or more compounds with the same molecular formula but with different configurations; and because of molecular asymmetry they rotate plane polarized light. A compound that rotates plane polarized light is said to be optically active. For a compound to be optically active, it must have a carbon atom which is substituted by four different groups, and this carbon atom is called CHIRAL CARBON ATOM e.g. as in lactic acid.
The compound and its mirror images must not be super imposable on each other. When the compound rotates the plane polarized light to the right, it is said to be DEXTROROTATORY and is represented by d- or (+). When the compound rotates the plane polarized light to the left, the compound is LAEVO-ROTATORY and is represented by L- or (-).

EVALUATION:
i. Use two sets of structural formulas to explain geometric isomerism.
ii. Briefly explain what is meant by chiral carbon atom.

ASSIGNMENT:
i. What makes a compound to be optically active?
ii. What is dextro-rotation?
iii. What is laevo-rotation?

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