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Organic
chemistry review
Francine
Taylor-Campbell, Contributor
Points
to note
- Polymerisation
is the formation of a large molecule
from smaller units called monomers.
- Monomers
containing the C=C can add together
to form polymers (addition) or two
units can react together to eliminate
a small molecule such as water (condensation).
- Polysaccharides
such as starch can be broken down
to simple sugars (monosaccharides)
by enzymes (such as amylase) or
during acid hydrolysis.
- Proteins,
polyesters and polyamides are all
formed from condensation polymerisation.
- Hydrolysis
is the breakdown of large molecules
to small ones by reaction with water.
This can be done in the presence
of an acid.
- When
sugars are fermented in the absence
of oxygen, ethanol is produced.
- Fractional
distillation can be used to produce
pure ethanol from the products of
fermentation.
We
will continue our revision by examining
some questions on the topic.
2.
(a) The following terms are used in
the description of organic compounds:
alcohol alkane alkene amide hydrocarbon
polymer
From
the list, choose two terms which can
be applied to each of the compounds
given below.
(i)
methane
(ii)
hexene
(iii)
poly(ethene)
(iv)
nylon
(b)
One of the general characteristics
of homologous series is that all the
members can be represented by a general
formula.
(i)
What is the general formula of the
alkane series?
(ii)
Give one other characteristic of homologous
series.
ANSWERS
2.
(i) Methane - alkane and hydrocarbon
(ii)
Hexene - alkene and hydrocarbon
(iii)
Poly(ethene) - alkane and polymer
(iv)
Nylon - amide and polymer
(b)
General formula alkane: CnH2n+2n
(ii)
Other characteristics of homologous
series are:
Each
consecutive member differs by a -CH2
group.
The
members show similar chemical reactions.
1.
Study the reaction scheme below and
use it to answer the questions given.
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Glucose
=
(FERMENTATION)
=
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P
=
(DEHYDRATION)
=
Ethene,
C2H4
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=
(BROMINE)
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Ethene,
C2H4
=
(HYDROGEN/CATALYST) =
R
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Ethene,
C2H4
=
(POLYMERISATION) =
Q
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(a)
(i) Give the names of the substances
and conditions needed to ferment glucose.
(ii)
Give the name of the gas that is produced
during the fermentation of glucose.
Describe a chemical test for the gas.
(b)
Give the name and molecular formula
for P
(c)
(i)What conditions are needed to to
convert P to ethene?
(ii)
Give the names of substances Q and
R.
(iii)
Write an equation for the reaction
between ethene and bromine. What type
of a reaction is this?
ANSWERS
1.
Glucose is fermented in the absence
of oxygen by yeast to give ethanol:
C6H12O6
(aq) ====== 2C2H5OH(aq)
+ 2CO2 (g) --- yeast
(ii)
The gas that is produced is carbon
dioxide, CO2
Carbon
dioxide produces a white precipitate
when bubbled through calcium hydroxide
(lime water):
Ca(OH)2
(aq) + CO2 (g) ====== CaCO3
(s) + H2O (l)
(b)
Substance P is ethanol. Formula: C2H5OH
(ii)
Ethanol can be converted to ethene
by catalytic dehydration using concentrated
sulphuric acid at 170 0Cor by passing
the gas over hydrated alumina (Al2O3).
(c)
Substance Q is polythene/poly(ethene),
a polymer of ethene, and substance
R is ethane formed from the addition
of hydrogen to ethene:
(ii)
C2H4
(g) + Br2
==== C2H4Br2
(l)
This
is an example of an addition reaction.
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There
is always something new to learn
during cosmetology classes at
Denbigh High School.
photo Michael Lee
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Francine
Taylor-Campbell is an independent
contributor.
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