OCR F332 Polymer Revolution

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Chemistry of Natural Resources: Polymer Revolution
Bonding and Structure
(a) explain how hydrogen bonds form and describe and give examples of hydrogen bonding, including in water
and ice
Hydrogen bonding is the strongest intermolecular force . They only form when hydrogen is
covalently bonded to fluorine , nitrogen or oxygen as they are very electronegative.
For hydrogen bonding to occur, the molecules involved must have the three following features:
A large dipole between an H atom and a highly electronegative atom such as O, N or F
The small H atom can get very close to the O, N or F atoms in nearby
A lone pair of electrons on the O, N or F atom, with which the positively
charge H can line up
Ice consists of a regular hexagonal structure which means it is less dense than
water. Ice has more hydrogen bonds than liquid water and as these bonds are
relatively long it means the water molecules are further apart, making it less dense
than water.
(b) explain the relative boiling points of substances in terms of intermolecular bonds
To boil a liquid, you need to overcome the intermolecular forces , so that the particles can escape from the liquid
surface. You need more energy to overcome stronger intermolecular forces so they therefore have higher boiling
points . Substances that form hydrogen bonds have higher boiling and melting points than other similar molecules
with no hydrogen bonds, because of the extra energy needed to break the hydrogen bonds.
A dipole is a molecule (or part of a molecule) with a positive end and a negative end. Molecules that have dipoles
are said to be polarised. There are 3 types of dipoles:
Permanent Dipoles Instantaneous Dipoles Induced Dipoles
This occurs when two atoms are These are only temporary and arise If an unpolarised molecule finds
bonded together and have when the electron density is not itself next to a dipole, the
substantially different evenly distributed around the unpolarised molecule may get a
electronegativities e.g. HCl and H2 O
whole molecule e.g. when two
dipole induced in it e.g. Cl2 coming
chlorine atoms are close to each close to HCl
3 kinds of intermolecular bonds can form from these dipoles:
Permanent dipole permanent dipole
Permanent dipole induced dipole
Instantaneous dipole induced dipole
(c) describe and explain the solubility of a dissolving polymer based on poly(ethanol) (or other polymers, given
information) in terms of its molecular structure: insoluble when very many or very few internal hydrogen bonds,
soluble when an intermediate number of hydrogen bonds
A substance will dissolve in water if the molecules of the substance are able to form hydrogen bonds with the
water molecules instead of with each other. For example poly(ethanol) forms hydrogen bonds with water,
allowing it to dissolve.
If a molecule has lots of hydrogen bonds or very few hydrogen bonds = insoluble
If a molecule has not too many and not too few (intermediate) hydrogen bonds = soluble

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Chemistry of Natural Resources: Polymer Revolution
Position of OH group Example
Primary At the end of the chain the OH is attached to a Ethanol
carbon bonded to 2 hydrogens
Secondary In the middle of the chain the OH is attached Butan2ol
to a carbon bonded to 1 hydrogen
Tertiary The OH is attached to a carbon bonded to no 2methylbutan2ol
Organic Reactions
(g) describe and explain the technique of heating under reflux for reactions involving volatile liquids
Oxidising Primary Alcohols:
1.…read more

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Chemistry of Natural Resources: Polymer Revolution
This involves the removal of one molecule from another. For example, ethanol can make ethene and water.…read more

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Chemistry of Natural Resources: Polymer Revolution
heat and
(k) describe and explain the following properties of alcohols:
(i) oxidation of alcohols to carbonyl compounds (aldehydes and ketones) and carboxylic acids with
acidified dichromate (VI) solution, including the importance of the condition (reflux or distillation) under
which it is done
Alcohols can be oxidised by using an oxidising agent. You can use acidified dichromate (VI) solution as the
oxidising agent to oxidise alcohols.…read more

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Chemistry of Natural Resources: Polymer Revolution
Reaction Mechanisms
(l) explain and use the terms:
Addition Where two or molecules react to form a single larger molecules
Electrophile A positive ion or molecule with a partial positive charge that will be attracted to a negatively
charged region and react by accepting a lone pair of electrons to form a covalent bond
Carbocation A positively charged carbon atom that has a share in only 6 outer electrons making it very
use the mechanism of electrophilic addition…read more

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Chemistry of Natural Resources: Polymer Revolution
In the E/Z system, Br has a higher priority than F and CH 3 has a higher priority than H.
If the two carbon atoms have their 'higher priority group' on
opposite sides, then it's an E isomer .
If the two carbon atoms have their 'higher priority group' on
the same side, then it's a Z isomer .…read more

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