Topic 20 - Organic chemistry. Introduction- functional groups and naming Nucleophilic substitution reactions Elimination reactions Condensation reactions Reaction pathways Stereoisomerism. 20.1 Ester. Functional group: -COOC- Condensation reaction or esterification
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(The underlined forms water)
Nucleophiles and electrophiles- oftenneeded in organicreactions
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
Monomolecular = one species in the rate determining step. Rate = k [org]
Heterolytic fission of substrate rate determining step
Formation of inermediate carbocation
Racemix mixture formed
C-I > C-Br > C-Cl > C-F (cf. bond strength)
CN- > OH- > NH3 > H2O
R-X + CN-
R-CN+ X-Forming a nitrile
The carbon chain will be prolonged with one carbon atom
CH3CH2-CN + H2/Ni CH3CH2-NH2
CH3CH2-CN + H+/H2O CH3CH2-COOH
Condition: Hot and concentrated sodium hydroxide solution in ethanol. Reflux.
CH3CH2-Br + OH- CH3CH2-OH + Br-
Will happen in warm dilute solution of sodium hydroxide, the hydroxide ion will work as a nucleophile.
Name: R-yl R’-oate
Esters: flavouring agents (food, perfume), solvents, plastics (polyesters)
Cancondensewith a diol
Cancondensewith a dicarboxylicacid
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
hexanedioicacid + 1,6-diaminohexane Nylon
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 quarternaryammonum 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
Ethanoic acid, CH3-COOH : Methyl methanoate HCOOCH3
Propanal, CH3-CH2-CHO : Propanone, CH3-CO-CH3
m.p= 286oC m.p.= 130oC with decomposition.
Strong H-bond between molecules in trans. Strong H-bond in the molecule in cis.
enantiomers to each other
enantiomers to each other
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.