Unit 3 Chemistry – Reactions of Functional Groups
Reactions of chloro-alkanes


the presence of a highly electronegative Cl atom makes the chloroalkane a polar
molecule
the chlorine draws electrons away from its attached carbon, making the carbon
susceptible to attack from negative ions, such as hydroxide ion OHchloromethane
H
H – C+– Cl–
H
–
OH
CH3OH + Clmethanol
hydroxide
R–Cl
+
OH-

R-OH
+
Cl-

chloroalkane
hydroxide
alkanol
this reaction is a substitution reaction … OH being substituted for Cl

polar molecules, such as water H2O and ammonia NH3 can also attack the C-Cl bond
-----------------------------------------------------H
chloroethane
H3C – C+– Cl–
H
NH3
CH3CH2NH2 + HCl
aminoethane
ammonia
R–Cl
+
chloroalkane
NH3 
ammonia
R–NH2
+
HCl
amine
--------------------------------------------------------------chloroethane
H
H3C – C+– Cl–
H
OH2
CH3CH2OH + HCl
ethanol
water
R–Cl
chloroalkane
+
H2 O
water

R–OH
+
HCl
alkanol
--------------------------------------------------------
Reactions of Alkanols


ethanol has a highly polar molecule and is soluble in water
alkanols, like ethanol, can undergo substitution reactions …
methanol
H
silica catalyst
H – C – OH
CH3NH2 + H2O
H
aminomethane
NH3
ammonia
R–OH
+
alkanol
NH3

ammonia
R-NH2
+
H2O
amine
-------------------------------------------------------


primary alkanols are oxidised to carboxylic acids
a primary alcohol is one in which the OH group is attached to the end of the alkyl
chain [or the end of an alkyl side chain]
atmospheric oxygen can be the oxidant, but acidified dichromate or permanganate
are the preferred laboratory oxidants
CH3CH2OH(aq)
[O2]
ethanol in wine
CH3COOH(aq)
vinegar, so cork your wine!
Note: the equation above is not a balanced redox equation … it is simply a
schematic representation of the reaction path from alkanol to carboxylic acid
CH3CH2CH2OH(aq)
1-propanol
[Cr2O72-/H+]
CH3CH2COOH(aq)
propanoic acid
------------------------------------------------------------------------Reactions of Carboxylic Acids

all carboxylic acids are weak acids, partially ionizing in water to form a weakly acidic
solution
CH3COOH(aq) + H2O(l)  CH3COO-(aq) + H3O+(aq)

being acids, carboxylic acids react with bases, reactive metals and carbonates
R-COOH(aq) + NaOH(aq)  R-COO.Na(aq) + H2O(l)

carboxylic acids react with alkanols to produce esters [esterification reaction]
Esters


esters are volatile organic compounds [smells or flavours]
esters contain the ester functional group and have the general structure …
-CO-O-R
ester functional
group
Forming Esters [condensation reaction; esterification]

esters are formed by the condensation reaction between a carboxylic acid and
alkanol [ sulfuric acid often used as a catalyst]
H2SO4 catalyst
R-COOH(aq) + HO-R’(aq)
carboxylic acid
R-COO-R’(aq) + H2O(l)
alkanol
ester
water

the reaction is called a condensation reaction because water is a product

esters are named by replacing the “anol” of an alkanol with “yl” and the “ic
acid” of the carboxylic acid with “ate”
propanol + ethanoic acid
propyl ethanoate
In the name, the alkanol name
comes first, but sthe structure is
usually shown with the carboxylic
acid to the left.
Polyesters

a polyester is a copolymer made by the condensation polymerisation of a di-acid
with a diol …
HOCH2OH + HOOCCH2COOH + HOCH2OH + HOOCCH2COOH + etc. etc.
diol
di-acid
diol
… OCH2O-OCCH2CO-OCH2O-OCCH2COO…
polyester polymer
di-acid
+ lots H2O
Reactions of Functional Groups
1. Using structural formulas for the reactants and products, illustrate the
following organic reactions:(a) propan-1-ol, from 1-chloropropane
(b) 2-aminobutane, from 2-chlorobutane
(c) aminoethane, from ethanol
------------------------------------------------------------------------2. Butanoic acid can be formed from butan-1-ol.
(a) Name the reaction involved in converting butan-1-ol to butanoic acid.
(b) Name suitable reactants that could be used to facilitate this change.
(c) Explain why butan-2-ol cannot be oxidised to form butanoic acid.
------------------------------------------------------------------------3. Write an equation illustrating that CH3CH2CH2COOH(aq) is a weak acid.
------------------------------------------------------------------------4. Synthetic pineapple flavour is the organic compound, ethyl butanoate.
(a) Name the two reactants used to produce ethyl butanoate.
(b) Name the type of reaction [give 2 alternative names] involved in the
formation of synthetic pineapple flavouring.
(c) Using structural formulas for all reactants and products, illustrate the
formation of ethyl butanoate, including any catalyst employed
(d) On the structural formula of ethyl butanoate, highlight and name the
linking functional group.
------------------------------------------------------------------------5. Using structural formulas for all reactants and products, illustrate the
formation of synthetic rum flavour, ethyl methanoate.
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