Download File - Mr Francis` Weebly

Organic Chemistry
The World of Carbon
Bonding
• In this topic the majority of the bonding you
will encounter will be covalent.
• We can represent this with either an electron
dot diagram or a line between atoms (-).
• A hydrocarbon is a compound containing
hydrogen and carbon only.
• A carbohydrate contains carbon, hydrogen and
oxygen.
Bonding of Carbon
• Carbon can bond onto itself!
• Within organic chemistry carbon forms 4
bonds, this gives it a tetrahedral shape.
• Whenever you are counting the bonds a
carbon atom makes-look for 4!
• It has 6 electrons in its outer shell arranged
1s22s2sp2
• It has room for 4 bonds to 4 other atoms.
Bond angles
• (A)The carbon atom forms bonds
in a tetrahedral structure with a
bond angle of 109.5O.
• (B) Carbon-to-carbon bond angles
are 109.5O, so a chain of carbon
atoms makes a zigzag pattern.
• (C) The unbranched chain of
carbon atoms is usually simplified
in a way that looks like a straight
chain, but it is actually a zigzag, as
shown in (B).
• In effect, you draw zigzag chains
Prefixes
• These are the prefixes denoting the numbers
involved in carbon chains (YOU MUST LEARN
THESE).
• Meth-1
Eth-2
Prop-3
But-4
• Pent-5
Hex-6
Hept-7
Oct-8
• Non-9
Dec-10
Hydrocarbons
• The most commonly used fuels are
hydrocarbons.
• There are 4 main groups you are expected to
know in Chemistry 2AB.
• Alkanes
Alkenes
• Cycloalkanes
Cycloalkenes
• In addition to this you will learn an array of
functional groups, giving you a large amount
of compounds to learn to name.
Alkanes
• Alkanes are saturated hydrocarbons. This
means that all of the bonds are single bonds.
• They cannot undergo addition reactions but
can take part in elimination and substitution
reactions.
• Alkanes are based on a hydrocarbon chains.
• They all end with the suffix –ane.
• General formula is CnH2n+2
Alkenes
• These are unsaturated hydrocarbons. They
have at least 1 double Carbon to Carbon bond
which can be added to.
• Can undergo addition, elimination and
substitution reactions.
• Suffix is –ene. If more than one –diene, -triene
etc.
• General formula is CnH2n but H can be less
depending on number of double bonds
Alkynes
• Unsaturated hydrocarbon containing a triple
Carbon to Carbon bond.
• Same rules as alkenes.
• Suffix is -yne
• General formula is CnH2n-2
Cycloalkanes
• Saturated hydrocarbons in which the main
body is a ring structure.
• Cyclo is placed as a prefix and then the
compound is named like an alkane.
• General Formula is CnH2n
Cycloalkenes
• Unsaturated hydrocarbons in which the main
body is a ring structure.
• Cyclo is placed as a prefix and then the
compound is named like an alkene.
• General Formula is CnH2n-2
Cycloalkynes
• Unsaturated hydrocarbons in which the main
body is a ring structure.
• Cyclo is placed as a prefix and then the
compound is named like an alkyne.
• General Formula is CnH2n-4
Alkanes
Cycloalkanes
• (A)A straight-chain
alkane is identified by
the prefix n- for
"normal" in the
common naming
system.
• (B) A branched-chain
alkane isomer is
identified by the prefix
iso- for "isomer" in the
common naming
system. In the IUPAC
name, isobutane is 2methylpropane.
(Carbon bonds are
actually the same
length.)
• (A)The "straight" chain
has carbon atoms that
are able to rotate
freely around their
single bonds,
sometimes linking up
in a closed ring. (B)
Ring compounds of
the first four
cycloalkanes.
Aromatic Hydrocarbons
• Aromatic hydrocarbons are ring structured
hydrocarbons in which there are delocalised
π-electrons in the ring.
• π electrons are unpaired electrons in the
plane of the benzene ring.
• These electrons make the compound more
stable than expected.
• Aromatics undergo substitution reactions.
Benzene
Petroleum
• Crude oil is a mixture of various hydrocarbons.
• It is formed from the fossilised remains of
marine organisms.
• These organisms die and fall to the bottom of
the ocean where they are covered in silt.
• Over time and under extreme pressure and
heat, without oxygen, they turn into crude oil.
• Crude oil is processed by Fractional
Distillation.
Fractional Distillation Column
•Crude oil is fed
through a tube
towards the column.
•The tube is heated
using a furnace.
•Each fraction is
separated in the
column by it’s
approximate boiling
point.
Fractions
• The octane rating
scale is a
description of
how rapidly
petroleum burns.
It is based on (A)
n-heptane, with
an assigned
octane number of
0, and (B) 2,2,4trimethylpentane,
with an assigned
number of 100.
Hydrocarbon Derivatives
• Introduction
– Hydrocarbon derivatives are formed when one or more
hydrogen atoms is replaced by an element or a group of
elements other than hydrogen.
– Halogens (F2, Cl2, Br2, I2,) can all add to a hydrocarbon to
form am alkyl halide.
•
•
•
•
•
When naming the halogen the –ine ending is replaced by –o
Fluorine becomes fluoro
Chlorine becomes chloro
Bromine becomes bromo
Iodine becomes iodo
• Common examples of organic halides.
– Alkenes can also add to each other in an addition
reaction to form long chains of carbon compounds.
• this is called polymerization
– The atom or group of atoms that are added to the
hydrocarbon are called functional groups.
• Functional groups usually have multiple bonds or lone
pairs of electrons that make them very reactive.
• Alcohols
– An alcohol has a hydrogen replaced by a hydroxyl (-OH)
group.
– The name of the hydrocarbon that was substituted
determines the name of the alcohol.
– The alcohol is named using the hydrocarbon name and
adding the suffix –ol.
• If methane is substituted with an OH group it
becomes methanol
• If a pentane group is substituted with an OH group it
is pentanol.
• For alcohols with more than two carbon atoms we
need the number the chain so as to keep the alcohol
group as low as possible.
• Four different alcohols. The IUPAC
name is given above each
structural formula, and the
common name is given below.
• Gasoline is a mixture of hydrocarbons (C8H18 for example)
that contain no atoms of oxygen. Gasohol contains ethyl
alcohol, C2H5OH, which does contain oxygen. The addition
of alcohol to gasoline, therefore, adds oxygen to the fuel.
Since carbon monoxide forms when there is an insufficient
supply of oxygen, the addition of alcohol to gasoline helps
cut down on carbon monoxide emissions. An atmospheric
inversion, with increased air pollution, is likely during the
dates shown on the pump, so that is when the ethanol is
added.
– The OH group is polar and short chain alcohols are
soluble in both nonpolar alkanes and water.
– If an alcohol contains two OH groups it is a diol
(sometimes called a glycol).
– An alcohol with three OH groups is called a triol
(sometimes called a glycerol).
• Common
examples of
alcohols with
one, two, and
three hydroxyl
groups per
molecule. The
IUPAC name is
given above each
structural
formula, and the
common name is
given below.