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Organic Compounds
Organic Compounds
Organic compounds are those compounds found in any
organism that is living or was once living
compounds from never living substances are referred to as
“inorganic”
Chemical Definition:
Organic Compound – any compound that contains the
element carbon
-- The definition has also changed because organic
compounds can now by synthesized in laboratories
What it does not include
•Carbon Monoxide
•Carbonates
•Hydrogencarbonates
What else ?
• Can contain
–Hydrogen (Most do)
–Oxygen (many do)
–Nitrogen (some do)
–Halogens (some do)
Carbon’s Bonding Pattern
• Carbon has 4 electrons in its outer shell. To
satisfy the octet rule, it needs to share 4
other electrons. This means that each
carbon atom forms 4 bonds.
• The 4 bonds are in the form of a
tetrahedron, a triangular pyramid.
• Carbon can form long chains and rings,
especially with hydrogens attached.
• Compounds with just carbon and hydrogen
are “hydrocarbons”: non-polar compounds
like oils and waxes.
Bonding in Organic Compounds
• Usually covalent with
single bonds being sigma
(σ) type if all bonds are
single the compound is
said to ne saturated
• Compounds with Double
/ triple bonds are said to
be unsaturated and
contain one sigma and
the rest Pi (π) bonds
Pi Bond
Sigma Bond
Bonding in Organic Compounds
• Aromatic compounds
with a benzene ring have
a special mixed type of
bonding (explained later)
• Organic compounds with no
benzene ring is said to be
aliphatic
Classification
• Important when there are:
• 7 million Organic Compounds
• 1.5 million Inorganic Compounds
Classification
• Grouped into families called
homologous series
• Each series has a general
formula and specific chemical
properties
Classification
• After that we classify according to
structure
–Look at the central (key) Carbon atoms
and depending on if they are
tetrahedral or planer...we know things
about the compound
Tetrahedral Carbon
Methane is Tetrahedral
0
109.5
H
C H
H
H
4 equivalent C-H bonds (s-bonds)
All purely single bonds are called s-bonds
Methane is Tetrahedral
0
109.5
The shape is explained by the mutual
repulsion theory
In saturated organic compounds all of the
carbon atoms are tetrahedral
We will be looking at
Alkanes
Chloroalkanes
Alcohols
Physical Properties of Alkanes
Non-polar molecules, which are less dense
than water.
Alkanes are immiscible with water making
two layers.
Van-der Waals or dipole-dipole
attractive forces, and not H-bonding (as
in polar molecules) are the main
intermolecular forces
Physical Properties of Alkanes
Alkanes show regular increases in bpt and mpt as
molecular weight increases down the homolgous
series
These weak intermolecular forces operate over
small distances, arising because the electron
distribution within molecules at any given instance
is not uniform. Resulting in tiny electrical
attractions between molecules.
These temporary dipoles hold alkanes as liquids
or solids, and must be overcome in order to
vaporize a liquid or melt a solid (wax)
Uses of Alkanes as fuels
• Useful due to their high heat of
combustion
• Natural gas = mainly Methane
• LPG = Propane and Butane
• Petrol = Mixture of hydrocarbons (5 – 10
C alkanes)
• Kerosene = 10 – 14 C alkanes used for
heating fuel and Jet fuel
Chloroalkanes
• Alkane with one or
more hydrogen atoms
replaced by a chlorine
atom
– e.g. methane to
chloromethane
– Note that the central
atom (C) is still
tetrahedral
• After the Hydrogen is replaced the remainder
of the molecule is known as an alkyl group
• In Methane CH3 is left (Methyl group)
• Other Alkyl groups include
–ethyl group
• In ethane C2H5 is left
–propyl group
• In propane C3H7 is left
–butyl group
• In butane C4H9 is left
• In other words they are named after the
alkane they are derived from
• Chloromethane
Chloro...........
indicates the
presence of a
Chlorine
atom
CH3Cl
• > 1 chlorine atom and we need another prefix
– Dichloromethane
CH2Cl2
• More than 1 chlorine atom and we need another
prefix
No. Cl Name of Compound
atoms
Chemical
Formula
1
Chloromethane
CH3Cl
2
Dichloromethane
CH2Cl2
3
Trichloromethane
CHCl3
4
Tetrachloromethane CCl4
Structural Formula
• More than 1 carbon and we need to:
• Indicate the position of the chlorine atom on
the chain
• Name from the chlorine end with one
exception*
2
•*Either end will be C=1
•But > 1 Cl atom and you must
number
1
chloroethane
• Example 15.1 (a)
(write up for homework)
• Name and draw the structural formula for
CH2ClCH2Cl
• Naming: CH2ClCH2Cl
• 2 chlorines so it starts with di• One chlorine atom attached to each carbon so
we need to number .....1,2
• Derived from the alkane ethane
• Name= 1,2 dichloroethane
• Example 15.1 (a)
• Name and draw the structural formula for
CH2ClCH2Cl
Try this one on your own
Example 15.1 (b)
• CH3CCl3
3 chlorines so starts
with tri-
All 3 are on the same
carbon so when we
number they all
receive the same
number
Derived from ethane
Hence:
1,1,1 trichloroethane
What if it’s a propane or a butane derivative
• Same rules apply...see example 15.2 (a-e)
CH2CHClCH3
1 chlorine so starts with just
chloro
on the 2nd carbon so when
we number
Derived from propane
Hence:
2, chloropropane
• What’s this:
• CH2ClCH2CH3
• Or this
• CH3CH2CH2Cl
OR
Why
• 1 chlorine atom so we start at chloro
• Attached to the first carbon so we
number = 1
• Remember we number from the chlorine
• Derived from propane (C3H8)
• Hence: 1, chloropropane
Another example
• CH3CH2CHClCH3
• 1 chlorine
attached at
carbon 2
• Derived from
butane (C4H10)
• Hence:
2, chlorobutane
Butane
2, chlorobutane
Homework
• Copy out Examples 15.2 a - e
Physical State and Properties
• Carbon – Chlorine bond is polar
• Chloroalkanes are insoluble in H2O
• Soluble in non polar solvents (cyclohexane &
methylbenzene)
• Higher BP than other alkanes (polar nature)
• Higher BP is also found in longer chain
molecules
• Most are liquid except for Chloroethane and
chloromethane (gases)
BP of Chloroalkanes containing one chlorine atom increases as the
carbon chain increases
BP
Carbons
Physical State and Properties
Chloroalkane
BP(K)
Chloromethane
Chemical
Formula
CH3Cl
Chloroethane
CH3CH2Cl
285
1-Chloropropane CH3CH2CH2Cl
1-Chlorobutane
249
320
CH3CH2CH2CH2Cl 352
Chloroalkanes are used as solvents (dry cleaning)
Alcohols
• Homologous series with general formula
CnH2n+1OH
• All alcohols have an OH functional group
• OH replaces an Hydrogen atom in the alkane
• All the carbons are tetrahedral in shape
• Named by replacing e of alkane with ol
Alcohols
• If there is more than 3 carbons we need to
indicate where the OH (hydroxyl) group is
• If its positioned at the end then this gets
priority and is given the prefix 1
• The carbon attached to this OH grp will have
no more than one carbon bonded to it
(except in Methanol where it is bonded to 3 hydrogen atoms)
Carbon attached t only 1 other carbon
• These alcohols are called Primary Alcohols
here are the first 4
Methanol
Ethanol
Propan – 1 - ol
Butan – 1 - ol
Homework
• Draw table 15.3
Secondary Alcohols
• Have 2 carbons attached to the carbon with
the OH group............example Propan – 2 - ol
Carbon attached to 2 other carbons
Example 15.4
• Write the name and structural formula for the
secondary alcohol containing four carbons
• If its a secondary alcohol then the primary
carbon cannot be at the end so.....
Example 15.4
• As it has 4 carbons it does not matter which of
the middle two contain the hydroxyl (OH) grp
so we just name the carbon with this group
“2”
Example 15.4
• The name is decided by the alkane grp it is
derived from (butane), the OH group makes it
butanol and the position of the OH makes it
butan – 2 - ol
Physical State and Properties
Alkane
Formula
BP (K) Alcohol
Formula
BP(K)
Ethane
C2H6
184
Methanol
CH3OH
338
Propane
C3H8
231
Ethanol
C2H5OH
351
(gas @RT)
(Liq @RT)
Butane
C4H10
272
Propan-1-ol C3H7OH
371
Pentane
C5H12
309
Butan-1-ol
390
C4H9OH
Because of hydrogen bonding and dipole-dipole interaction alcohols have different
properties to Alkanes
Boiling point (K)
Alcohols
Alkanes
Alcohols have a much
higher BP than alkanes
even though they have
a similar Mr
Relative Molecular Mass
An alcohol may be thought of as a
compound very similar to a water
molecule which has replaced an
hydrogen atom with an alkyl group
We refer to the alkyl group by the letter “R”
σ-
σ+
Polar OH group results in hydrogen bonding
between molecules
More electronegative O2 (-ive charge) attracts
positively charged Hydrogen
The hydrogen bonds strengthen
the stability of the molecule and
so it remains liquid at room
temperature
The hydrogen bonds need to be
broken before it can become a
gas and this takes more energy
hence raising the BP
Wines and beers are mixtures of
ethanol and water
They mix due to hydrogen
bonding between Oh groups in
each
Solubility decreases as the
hydrocarbon chain increases
Occurrences and Uses
Most ethanol is made by hydration
of ethene
+
HOH
water
ethene
Ethanol
Fermentation of alcohol
Ethanol in drinks like wine is made by
fermentation of sugars in fruits
Involves a series of biochemical reactions
requiring enzymes found in yeast
The enzymes break down the sugars to give
ethanol and carbon dioxide
Fermentation of alcohol
C6H12O6 (aq)
2C2H5OH (aq) + CO2 (g)
The process is anaerobic to avoid the
oxidation of ethanol to ethanal and
ethanoic acid
Brewing
Used to make beer – raw material malted
grain
End result is alcohol content of 3 – 5% v/v
ethanol
Whiskey is made from fermented malted
barley which is ten distilled to concentrate the
alcohol to about 40% v/v ethanol
Fuel
Fermentation of sugar cane
makes ethanol and then mixed
with petroleum products to make
a motor fuel instead of petrol
Solvent
Ethanol is a very good solvent that
evaporates easily
Used in paints, glues, perfumes,
aftershave
Methylated spirts ...mostly ethanol
with a little methanol and dye
(poisonous)
Planer Carbon
Ethene
C2H4
• Ethene is a planer molecule
• Planer carbon atoms are a feature of many
homologous series
• C=C or C=O bonds demonstrate a planer
atoms although other carbon atoms in the
molecule may be tetrahedral
• Double bonds mean the molecule is
unsaturated
We will be looking at
Alkenes
Aldehydes
Ketones
Carboxcylic acids
Esters
Aromatic compounds
Alkenes
• Homologous series of hydrocarbons
(CnH2n.)
• Unsaturated (C=C)
• First three members are gases @ RT
• Longer chains are liquids and solids
• Increase in BP as the carbon chain
increases
• Ethene is the first member
• Alkenes are Important industrial
chemicals...especially ethene
• Much more reactive than alkanes
• Ethene C=C double bond can undergo
addition reactions
• Ethene (alkene) by addition of itself can become a very long
chain alkane
• More on addition reactions later
Aldehydes
• Homologous series of hydrocarbons
(CnH2n+1CHO) where n = 0,1,2,3,etc...
• All contain a carbonyl group C=O )polar
covalent double bond)
• In aldehydes there is always an Hydrogen
atom bonded to the carbonyl group
• In Methanal (HCHO) the carbon found in
the carbonyl group is the only one in the
molecule
• The Carbonyl carbon is planer
• The functional group of the aldehydes is
CHO
• Aldhydes are names by replacing the e at
the end of the relevant Alkane with al
• Molecular formula is found by replacing
the last carbon in the chain from being
part of a Methyl
group to being
part of a CHO
group
Example 15.5
• Write the name and structural formula of the aldehyde
containing 2 carbons
• Base alkane is ethane (CH3CH3) so the name of the
aldehyde is ethanal
• Molecular formula is found by replacing the last carbon in the chain from
being part of a Methyl group to being part of a CHO group
• So.......CH3CHO
• Learn the first four aldehydes
Name of Aldehyde
Methanal
Ethanal
Propanal
Butanal
• Learn the first four aldehydes
Chemical Formula
HCHO
CH3CHO
CH3CH2CHO
CH3CH2CH2CHO
Methanal
Ethanal
propanal
Butanal
Physical State and Properties
• Presence of C+O means the molecule
is quite polar
• Dipole – Dipole attractions between
adjacent aldehyde molecules
• Higher BP than relevant alkane
• Lower BP than relevant Alcohol
•Methanal is Gas at RT
•Others are Liquids @ RT
• Hydrogen bonding between
aldehydes cannot occur
• Hydrogen is only bonded to
Carbon
• Polarity of the C=O bonds
mean that hydrogen bonding
can occur between water and
the CHO group
• Smaller aldehydes dissolve in
water
• The longer the chain the lower
the solubility
• Soluble in non polar solvents like
cyclohexane
Occurrences and Uses
• Found in nature
–Glucose
–Benzaldehyde....found in the
kernel of almond nuts
Ketones
• Homologous series with formula R1COR2
• R 1 and 2 are usually Alkyl groups
• All contain C=O (carbonyl Grp) as well, but
unlike aldehydes this group is in the centre of
the chain (no hydrogen bonded to the C=O
grp)
• Named by replacing the -e at the end of
the relevant alkane with –one
Alkyl Grp
Replaces CH2
• With 2 x alkyl groups and 1 x carbonyl
group there must be at least 3 carbons
• Molecular formula is found when the
central hydrogen atoms are replaced
with a C=O
Example 15.6
• Name the chemical formula and draw the
structural formula of the ketone containing 3
carbons
Example 15.6
• Corrosponding alkane is Propane so the
ketone is Propanone and the formula is
CH3COCH3
Name the first two ketones
• Learn the molecular and structural formula
Name of Ketone
Propanone
Butanone
Physical State and properties
• Similar properties to aldehydes
• Lower Ketones are soluble in water
• All are soluble in organic solvents
• Higher BP than relevant alkane
Occurrences and Uses
• Many are found in nature
• Testosterone & Progesterone....Human sex
hormones
• Butter, Ginger Oils and Spearmint,Nail varnish
Remover
Carboxylic Acids
• Homologous series, formula CnH2n+1COOH
(where n= 0,1,2,3,4,etc)
• COOH is functional group
• Structural formula is combination of a
Carbonyl grp and an hydroxyl group but
properties are distinctive
Carboxylic Acids
• Named by replacing the -e on the
alkanee with –oic
• Molecular formula found by
replacing the last Methyl group with
COOH
Example 15.7
• Name and structural formula
for carboxylic acid with 2
carbons
• Name:
• Alkane to carboxylic = ethane
to ethanoic
Example 15.7
• Chemical Formula
–CH3COOH
Learn the first four
Name of Carboxylic Acid
Methanaoic
Ethanaoic
Propanaoic
Butanaoic
• Learn the first four aldehydes
Chemical Formula
HCOOH
CH3COOH
CH3CH2COOH
CH3CH2CH2COOH
Homework
• Draw the four structural formula
Physical State and Properties
• Lower Carboxylic acids are colourless with
distinctive smell
• BP higher than relevant alkane and alcohols
• Higher BP due to formation of hydrogen
bonding resulting in dimers (2 carboxylic acids held
together by hydrogen bonds)
Physical State and Properties
Alkyl Grp or H
Alkyl Grp or H
Hydrogen bonded dimer
• Hydrogen bonding also happens
in water with lower carboxylic
acids
• Up to 4 carbon carboxylic acids
are highly soluble in water but as
the chain lengthens the solubility
decreases
Occurrences and Uses
• Methanoic aacid is the iritating fluid
used by ants and nettles
• Countermeasure is Sodium
hydrogencarbonate found in Bread
soda (weak base)
Occurrences and Uses
• Ethanoic acid
–Ethanol oxidises to ethanoic acid
.....spoiling wine
–Process used to make vinegar
–Manufacture of cellulose acetate
(varnish, lacquer, rayon)
Occurrences and Uses
• Propanoic acid
• Benzoic acid
• Sodium Benzoate (a salt of Benzoic
acid)
Used in food preservation
Esters
• Derived from Carboxylic acids
(not alkanes)
• Represented as R1COOR2
• Esters consist of 2 parts
1. An alkyl group derived from
an alcohol
2. R1COO from carboxylic acid
where “R” is either a
hydrogen atom or a alkyl
group
Formula is R1COOR2
• Naming is based on the 2 parts
• The alkyl group derived from the alcohol ...so
methyl, ethyl, propyl etc.....
• The carboxccylic acid ending in –oic which we
replace –oate
– Methanoic goes to methanoate
• Full thing: Methyl Methanoate
Example 15.8
• Name, Chemical and structural formula for
ester derived from ethanoic acid
(CH3COOH)and Methanol (CH3OH)
• Methyl
• Ethanoic
• Methyl ethanoate
Methyl
ethanoate
• Chemical Formula
• We write the acid first and leave out the last
Hydrogen so that we can add on the Alkyl
group
• Hence CH3COOH (carboxylic acid) is written
CH3COO
• The alkyl group (methyl, ethyl etc..) from the
alcohol is added
• Chemical Formula
• And we end up with the following for methyl
methanoate
• CH3COOCH3
• Structural formula follows the same rules
Ester linkage
Methyl Methanoate
Learn the esters containing four carbons
Name of Ester
Chemical Formula
Methyl Methanoate
HCOOH3
ethyl methanoate
HCOOC2H5
propyl methanoate
HCOOC3H7
Methyl ethanoate
CH3HCOOCH3
ethyl ethanoate
CH3HCOOC2H5
Methyl Propanoate
C2H5COOCH3
Homework
• Draw the structural formulas for the esters
containing four carbons
Physical State and properties
•
•
•
•
•
•
Methyl Methanoate
ethyl methanoate
propyl methanoate
Methyl ethanoate
ethyl ethanoate
Methyl Propanoate
All of these are liquids
C=O linkage is polar resulting
in intermolecular forces but
no actual hydrogen bonding
between adjacent esters
BP is the same as relevant
aldehyde and ketone
Hydrogen bonding can
happen in water due to polar
C=O (only with esters 5
carbons and under)
Soluble in non polar solvents
Occurrence and Uses
• Strong fruity smell
• Many occur naturally
– Fruit flavours (mango has 8 esters including ethyl
ethanoate)
• Artificial flavours in processed foods
• ethyl ethanoate used in paints and inks
• Fats and Oils are naturally occurring esters of
long chain Carboxyillic acid
Aromatic Compounds
• Derived from fractional distillation of crude oil
(benzene) and the Dehydrocyclisation of low
octane hydrocarbons
– (removal of hydrogen from straight chain
hydrocarbon to form benzene)
• Benzene – Planer six carbon ring structure
• 6 carbons in a
planer hexagonal
array
• Each C has a
valence of 4
– 1 with H
– 2 with C (σ)
– 1 free
• It was thought that there were 3 double
and 3 single bonds in the molecule but x
ray analysis shows that the bond lengths
are intermediate between single and
double
• The free electrons are said to be
delocalised ....not involved in the direct
sigma bonding of the molecule but
nevertheless connected using Pi bonding
• 6 valence electrons
are involved in a Pi
(π) bond spread
between the six
atoms in the ring
(shared)
• They form
overlapped orbitals
above and below
the carbon ring
Delocalised Pi bonding
• This is the
reason for
the circle in
the diagram
Physical Properties
• Non Polar means they are not soluble in water
• Soluble in non polar solvents
• Methylbenzene is a good solvent
Occurrences and Uses
• Benzene is carcinogenic
• Many are not...including aspirin
• Used in manufacture of dyes, detergents,
herbicides and medicines
• Acid – base indicators methyl Orange and
Phenolphtalein are aromatic compounds
Methyl Orange
Homework
• Draw structural formula from book
•
•
•
•
•
Phenolphthalein
Diurin
Folic Acid
Morphine
Martius Yellow
Organic Natural products
• Many examples
– Include carbohydrates and Steroids
– Derived from plant extracts and include perfumes,
dyes, medicines
– Modern techniques mean they can be isolated in
pure form
– Include; Aspirin, Morphine, Nicotine, Strychnine
and caffine
Experiment
• Extraction of Clove Oil from Cloves by Steam
distillation