INTRODUCTION TO ORGANIC CHEMISTRY ❑Organic compound ❑Organic reaction Noor Saadiah Mohd Ali BSc. (Hons), MSc., PhD. Chemistry Department CFSIIUM
Introductory Organic Compound Molecular & Structural Formula - Naming - Drawing Functional Group & Homologou s Series Isomerism Organic Reaction Types of Fission (Cleavage) Types of Reagent Types of Reaction
Molecular & Structural Formula Molecular Formula • Shows number of atoms for each element present in one molecule but does not show the arrangement of atoms Structural formula • Shows actual number of atoms and how they are bonded together
Structural Formula Expanded Structure: -show all atoms -type of covalent bond Condensed Structure: -hide C-H & C-C -branches is indicated in parentheses Skeletal Structure: -C&H are hidden unless they are part of the Func. Group 3-D Projection (Line-wedge-dash) - Only applicable for optical isomers
Types of Structural formulas expanded formula condensed formula skeletal formula H C H H C C C H H H H H H C H H H CH3CH2CH2CH2CH3 H C H H C C C H H H H H H OH OH CH3CH2CHCH3 OH CH3CH2CH(OH)CH3 C H H H C O C H H H CH3CCH3 O CH3COCH3 (CH3 )2CO O
6 A functional group is defined as an atom or a group of atoms that gives the organic compound its characteristic properties (chemical properties). Functional Groups • Organic compounds are classified by the presence of characteristic functional groups.
7 Homologous Series A homologous series is a series of organic compounds with similar chemical properties, in which each member differs from the previous on by the addition of a – CH2 – group CH4 C2H6 C3H8 C4H10 CH2 CH2 CH2
HOMOLOGOUS SERIES/FAMILY/ ORGANIC COMP FUNCTIONAL GROUPS NAMES OF FUNCTIONAL GROUPS IUPAC LAST NAME (SUFFIX) ALKANE -C-C- NONE -ANE ALKENE -C=C- DOUBLE BOND -ENE HALOALKANE -C-X HALIDES/HALO …O…-ANE ALCOHOL -C-OH HYDROXYL -OL PHENOL C6H5 -OH HYDROXYL -OL ALDEHYDE -C=O CARBONYL -AL KETONE -C=O CARBONYL -ONE CARBOXYLIC ACID -COOH CARBOXYL -OIC ACID ESTER -COOC- CARBOALKOXY -OATE ACYL CHLORIDE -COCl CARBOALKOXIDE -OYL CHLORIDE AMIDE -CONH AMIDO -AMIDE AMINE -NH2 AMINO -AMINE NITRILE -CN NITRILE -NITRILE Derivatives of -COOH Series of group which contain same func. group c c Group of atoms that give characteristic prop. Of organic comp To denote types of func. group c
9 Family General formula Functional group Example Formula IUPAC name Alkane CnH2n+2 RH (Nil) CH3CH3 Ethane Alkene CnH2n RCH = CH2 RCH = CHR R2C = CHR R2C = CR2 Carboncarbon double bond CH2 = CH2 Ethene Aromatic hydrocarbon ArH Phenyl group Benzene
10 Family General formula Functional group Example Formula IUPAC name Haloalkane CnH2n+1X RX ⎯ X halo group CH3Cl Chloromethane Alcohol CnH2n+2O CnH2n+1OH ROH ⎯ OH hydroxyl group CH3OH Methanol Aldehyde CnH2nO carbonyl group Methanal
New Way Chemistry for Hong Kong A-Level 3A 11 Family General formula Functional group Example Formula IUPAC name Ketone CnH2nO carbonyl group Propanone Carboxylic acid CnH2n+1COOH carboxyl group Ethanoic acid Amine RNH2 R2NH R3N amino group CH3NH2 Methylamine Nitrile RCN ⎯ C N nitrile group CH3CN Ethanenitrile
New Way Chemistry for Hong Kong A-Level 3A 12 Family General formula Functional group Example Formula IUPAC name Ester carboalkoxy Methyl ethanoate Acyl halide Carboalkoxide Ethanoyl chloride Amide amido group Ethanamide R = CnH2n+1 –
New Way Chemistry for Hong Kong A-Level 3A 13Identify the functional group(s) in the following compounds: (a) Answer (a) Carbon-carbon double bond ( ) and halo group (⎯Cl)
14Identify the functional group(s) in the following compounds: (b) Answer (b) Carbonyl group ( )
New Way Chemistry for Hong Kong A-Level 3A 15Identify the functional group(s) in the following compounds: (c) Answer (c) Amino group ( ) and carboxyl group ( )
16 State whether each of the following pair of compounds belong to the same homologous series. Explain your answer. (a) Answer (a) No, the first one is a carboxylic acid and the second one is an ester.
17 State whether each of the following pair of compounds belong to the same homologous series. Explain your answer. (b) Answer (b) Yes, both of them are alcohols.
18 State whether each of the following pair of compounds belong to the same homologous series. Explain your answer. (c) Answer (c) No, the first one is an amide and the second one is an amine.
19 (c) Identify and name the functional groups in the following compounds: Back (c) ⎯Br (halide), (carbonyl), (carboalkoxide), (aryl) Answer
Rules of IUPAC Name (Nomenclature) Determine the longest and continuous carbon chain with func. group (STEM+SUFFIX) Number the carbon with the lowest no. to func. group then to the prefixes For different prefixes, arrange them according to alphabetical order For identical prefixes use multiprefixes (di, tri or tetra) Separation rules: no. and no. are separated using comma while no. and letter are separated using hyphens PREFIX + STEM + SUFFIX 2-chloro-3-methyl 1,2-dichloro / 1,1,3-tribromo
Priority list for IUPAC Nomenclature Increasing priority Subordinate groups
C H H C H C H H H H C H H H Longest chain of carbons is three long propane Branch methyl 2-methylpropane Alkane Nomenclature
Practice C H H C H H C H H C H H H C H H H 2-methylbutane H H H H H C H C H H C C H C H H H C H C H H H 3-ethylpentane
Practice H C C C C C H H H H H H H H H H C H H C H H C H H H C H H heptane methyl 2-methyl 2- 2-methyl, 2-methyl heptane Sounds redundant 2,2-dimethylheptane
25 Cyclohexane methylcyclopentane 1,2-dimethylcyclohexane Cycloalkane
Alkene C C C C H H H H H H H H C H H C H H 3-methyl-1-pentene H H C C C C C H H H H H H H H C H H C H H 2-heptene H H C C H H H C H C H H 1-butene
Practice! methylpropene 2,4-dimethyl-2-pentene
Halides Nomenclature Cl Cl 2,3-dichlorohexane I I 3,3-diiodo-1-pentene
Alcohols Nomenclature OH C OH H H C H H H OH 2-propanol ethanol 1-cyclobutenol
Aldehydes Nomenclature C H H C H H C H H H C H O butanal C H H C Cl Cl C H H C H O C H H H 3,3-dichloropentanal
Ketones Nomenclature propanone 2-hexanone C H H C H H H C H O C H H C H H C H H C O C H H H C H H H
Carboxylic Acids Nomenclature C H H C H H C H H H C OH O Butanoic acid C H H C H H C F O HO 3-fluoropropanoic acid
Esters Nomenclature C H H C H H C H H C O C H H H C H H O H Secondary Branch Main Branch methyl pentanoate Methyl pentanoate
Esters- More examples.. C H H H C H H C O C H H O C H H C H H H C H H Butyl propanoate C H H H O H H C O C H H C C H H C H H H C H H Methyl hexanoate
Amines Nomenclature C H H N H H H methylamine C H H N C H H H H H dimethylamine
Isomerism -same molecular but different arrangement of atoms Constitutional (Structural) Isomerism Chain Isomerism Positional Isomerism Functional Group Isomerism Stereoisomerism Cis-trans (Geometrical) Isomerism Optical Isomerism ➢Same molecular ➢Different connection of atoms ➢Same molecular ➢Same connection of atoms ➢Different orientation ➢Same func. group ➢Differ in length of straight chain ➢Same func. group ➢Same length ➢Differ in position of func. group ➢Same molecular formula ➢Differ in func. group ➢Must contain C=C where each C attach to 2 different groups ➢Must contain chiral carbon
Draw all possible isomers for C5H10
Chain Isomerism ▹ Differ in the structure of their carbon chain (differ in the length of their straight chain or branches)
Positional Isomers ▹ Same carbon skeleton & homologous series ▹ Differ in the position of FG
Functional Group Isomers ▹ Same molecular formula but different FG ▹ Different homologous series CnH2nO CnH2nO2 CnH2n
Draw all possible isomers for C4H9Br
Isomerism -same molecular but different arrangement of atoms Constitutional (Structural) Isomerism Chain Isomerism Positional Isomerism Functional Group Isomerism Stereoisomerism Cis-trans (Geometrical) Isomerism Optical Isomerism ➢Same molecular ➢Same connection of atoms ➢Different orientation ➢Must contain C=C where each C attach to 2 different groups ➢Must contain chiral carbon
STEREOISOMERISM Molecules have the SAME MOLECULAR FORMULA but the atoms are joined to each other in a DIFFERENT SPATIAL ARRANGEMENT - they occupy a different position in 3-dimensional space. There are two types... • GEOMETRICAL ISOMERISM • OPTICAL ISOMERISM
GEOMETRICAL ISOMERISM cis-trans • an example of stereoisomerism • found in some, but not all, alkenes Occurs in compounds in which free rotation is prevented by the presence of a C=C • get two forms.... CIS Groups/atoms are on the SAME SIDE of the double bond TRANS Groups/atoms are on OPPOSITE SIDES across the double bond Isomers - have different physical properties - e.g. boiling points, density - have similar chemical properties - in most cases
GEOMETRICAL ISOMERISM RESTRICTED ROTATION OF C=C BONDS - Occurs in compounds in which free rotation is prevented by the presence of a C=C This produces two possibilities. The two structures cannot interchange easily so the atoms in the two molecules occupy different positions in space. Identify which structural of C4H8 that able to exhibit cis-trans isomerism
There are 3 isomers of C4H8 that are alkenes
GEOMETRICAL ISOMERISM Isomerism in butene There are 3 structural isomers of C4H8 that are alkenes*. Of these ONLY ONE exhibits geometrical isomerism. BUT-1-ENE 2-METHYLPROPENE cis BUT-2-ENE trans BUT-2-ENE
OPTICAL ISOMERISM •Optically active compound has ability to rotate plane polarized light • Organic compound will exhibit optical isomerism if it contains “chiral carbon” • two forms exist which are NON-SUPERIMPOSABLE MIRROR IMAGES of each other • non-superimposable means you you can’t stack one form exactly on top There are four different colours arranged tetrahedrally about the carbon atom 2-chlorobutane exhibits optical isomerism because the second carbon atom has four different atoms/groups attached CHIRAL CENTRES
OPTICAL ISOMERISM Spatial differences between isomers • Optically active compound has ability to rotate plane polarized light • Organic compound will exhibit optical isomerism if it contains “chiral carbon” • Two forms exist which are NON-SUPERIMPOSABLE MIRROR IMAGES of each other • Non-superimposable means you can’t stack one form exactly on top of the other Enantiomers @ Optical isomers
• 2-butanol • dichloromethane • 1,2-dibromo-1-chloroethane Optically active or inactive?