1. Topic 20 - Organic chemistry
Introduction- functional groups and naming
Nucleophilic substitution reactions
Elimination reactions
Condensation reactions
Reaction pathways
Stereoisomerism

2. 20.1 Ester Functional group: -COOC-
Condensation reaction or esterification
Many fruit-smelling esters
The bond in triglycerides (lipids)
Alcohol + carboxylic acid  ester + water
CH3-OH + HOOC-CH3  CH3OOC-CH3 + H2O
(The underlined forms water)

3. Esterification Name: => Methyl-buthanoate
Butanoic acid
Methanol
Name:
The alcohol part: Stem + yl: Methyl-
The acid part: the salt name; -buthanoate
=> Methyl-buthanoate

4. Which names?

5. Which names? Ethylethanoate propylethanoate
2-butylethanoate penthylpropanoate

6. Amine Relatives to ammonia => weak bases Functional group –NH2
H-bonds => higher bp’s, smaller ones are water-soluble etc.
Name: stem + suffix: -ylamine (or prefix amino-)
Methylamine CH3-NH2
Ethylamine CH3-CH2-NH2

7. Amide Functional group: -CONH Name: stem + suffix: -anamide
Methanamid H-CONH2
Ethanamid CH3-CONH2
Peptide bond in proteins

8. Nitrile Functional group: -CN Former name: cyanides
Name: stem + suffix: nitrile
Metanenitrile: HCN
Ethanenitrile: CH3-CN

9. Nucleophiles and electrophiles- often needed in organic reactions
Nucleophile- nucleus lover
Has free electronpair and whole or part negative charge
The larger the negative charge - the better the nucleophile
Eg: C=C, H2O, -OH, -CN, NH3
Electrophile-electron lover
Has whole or part positive charge
The larger the positive charge - the better the Electrophile
Eg: C=O, H+, C-Cl,

10. 20.2 Nucleophilic substitution reactions
Nu: + R-X  Nu-R + X:
It’s important to know the difference of these because they will undergo different forms of nucleophilic substitution reactions

11. SN2 or SN1?
SN2
SN1
Bimolecular = two species in the rate determining step. Rate = k [org]*[Nu]
Primary halogenoalkanes
Steric hindrance
One-step with transition state
Inversion of configuration
Monomolecular = one species in the rate determining step. Rate = k [org]
Tertiary halogenalkanes
Heterolytic fission of substrate rate determining step
Formation of inermediate carbocation
Racemix mixture formed

12. Factors affecting the rate
The halogen in the halogenoalkane is important for the reaction rate:
C-I > C-Br > C-Cl > C-F (cf. bond strength)
The stronger the nucleophile, the faster the SN2-reaction
CN- > OH- > NH3 > H2O

13. SN2 substitution reaction with ammonia
H3N: + R-X  R-NH2 + HX
Forming an amine

14. SN2 substitution reaction with CN- as nucleophile
R-X + CN- 
R-CN + X- Forming a nitrile
The carbon chain will be prolonged with one carbon atom

15. Reactions with nitriles
Nitrile + H2  Ni catalyst  Amine
CH3CH2-CN + H2/Ni  CH3CH2-NH2   
Nitrile + Acidic water  Carboxylic acid
CH3CH2-CN + H+/H2O  CH3CH2-COOH

16. 20.3 Elimination reactions
CH3CH2-Br + OH-  CH2=CH2 + H2O + Br-
Condition: Hot and concentrated sodium hydroxide solution in ethanol. Reflux.
Opposite to addition reaction
2 kinds; E1 and E2
If the conditions are different: A substitution reaction
CH3CH2-Br + OH-  CH3CH2-OH + Br-
Will happen in warm dilute solution of sodium hydroxide, the hydroxide ion will work as a nucleophile.

17. The E1 mechanism (similar to SN1)
Involves heterolytic fission of C-X bond
Tertiary halogenalkane
Via a carbocation intermediate

18. The E2 mechanism (similar to SN2)
Concerted bimolecular reaction
Primary halogenalkane
Via transition state

19. Dehydration reaction of alcohol to form alkene
E1 or E2?
Excess of H2SO4, ~170oC

20. 20.4 Condensation reaction
2 Organic molecules  1 Organic molecule + water
Acid catalysed
Esterification, etherification
Common in biochemistry, formation of polysaccharides, proteins, nucleic acids

21. Esterification Name: R-yl R’-oate
H2O
Name: R-yl R’-oate
Esters: flavouring agents (food, perfume), solvents, plastics (polyesters)

22. Amide condensation
Amine Carboxylic acid Amide Water
H2O

23. Polycondensations Plastics
Polyesters: polyethylene terphtalate (PET)
Polyamides; nylone

24. Monomers with two functional groups are required
Benzene-1,4-dicarboxylic acid + Ethane-1,2-diol
Can condense with a diol
Can condense with a dicarboxylic acid
Monomers with two functional groups are required

25. Polyamides HOOC-R-COOH + H2N-R’-NH2  H2N-R’-NH-OC-R-COOH
Di-amine amide bond
HOOC-(CH2)4-COOH + H2N-(CH2)6-NH2 
 HOOC-(CH2)4-CONH-(CH2)6-NH2 + water
hexanedioic acid ,6-diaminohexane  Nylon

26. Reaction pathways
1. Elimination reaction. Hot, concentrated and reflux 2. Substitution reaction. SN1 or SN2 3. Substitution reaction. SN1 or SN2. (Can be substituted up 4 times to a quarternary ammonum salt) 4. Condensation reaction. Acid catalyst (or alkaline catalyst, but more common when hydrolysis of ester). Equilibrium reaction. 5. Condensation reaction. Acid catalyst (or alkaline catalyst). Equilibrium reaction. 6. Nitrile to amin: Reduction with H2 and Ni-catalyst

27. Stereoisomerism
Different location in space of atoms or groups

28. Structural isomers Chain: e.g. n-butane : methylpropane
Positional: e.g. 1-propanol : 2-propanol
Functional groups:
Ethanoic acid, CH3-COOH : Methyl methanoate HCOOCH3
Propanal, CH3-CH2-CHO : Propanone, CH3-CO-CH3

29. Geometric
Double bond = p and s bonds. No free rotation around a double
cis-2-buten trans-2-buten
cis-1,2-dichloroethane: bp = 60.3oC
trans-1,2-dichloroethane: b.p. = 47.5oC

30. cis-but-2-ene-1,4.dioic trans-but-2-ene-1,4.dioic
m.p = 286oC m.p.= 130oC with decomposition.
Strong H-bond between molecules in trans. Strong H-bond in the molecule in cis.

31. Cyclic compounds can also give geometric isomers
Cis and trans

32. Optical
mirror plane
enantiomers to each other

33. Stereo isomers Different location in space.
Geometric
cis-2-buten trans-2-buten
Optical
mirror plane
enantiomers to each other

34. A carbon with 4 different substituents is said to have an asymmetric centre or to be chiral.
Chiral can also mean the whole molecule.
Enantiomers have the same physical properties except that they rotate the plane of polarised light in different directions.
Very important which form of the enantiomer in biology and medicine.

35. Polarimeter
Light: Electromagnetic radiation. Normal light oscillating in all directions.
Plane-polarized light: When normal light is sends throuhg a polarizing filter only waves in the same plan can pass. If two polarizing filters places 90o to each other the light will be compleataly blocked.
Polarimeter: Measure how much the light will rotate when pass through a solution with optically avtive substance. A sample holder between two filter