Functional groups The functional group of alkanes is the CC bond the alkenes CC bond and so on Tetrahedral carbon compounds In addition to the alkanes the other tetrahedral compounds are the ID: 371963
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Slide1
Functional Groups and PreparationsSlide2Slide3
Functional groups
The functional group of
alkanes
is the C-C bond, the alkenes C=C bond and so onSlide4
Tetrahedral carbon compounds
In addition to the
alkanes
the other tetrahedral compounds are the
Chloroalkanes
and the
AlcoholsSlide5
Chloroalaknes
Historically surgery was extremely painful and people only underwent surgery if it was absolutely essential
One of the early anaesthetics was Chloroform (CHCl
3
) (modern name tri-
chloro
methane)
Chloroform is an example of a
chloroalkanes
Chloroalkanes
are defined as compounds in which one or more of the hydrogen atoms in an
alkane
molecule have been replaced by a Chlorine atomSlide6
Chloroalkanes
have the same basic tetrahedral shape as the corresponding
alkanes
and like
alkanes
they are all saturated compounds
NB fig 22.1 p 341 for some common structures
They are rarely found naturally and are usually synthesised in a laboratorySlide7
Properties of Chloroalkanes
Most are liquid at room temperature
Their main use is as solvents
to remove oil and grease marks from machinery and in the dry cleaning of clothes
Paint stripper contains dichloromethane (can you draw this???)
They are insoluble in water
(due to having very little polarity)
They readily dissolve in non-polar solvents
such as
cyclohexane
They are suitable solvents for things such as
tippex
but they cause damage to the ozone layer so scientists are looking for alternativesSlide8
Naming Chloroalkanes
Find the parent chain of carbons and get the chain name (
ie
meth, eth, but)
Determine the carbon the chlorine is attached to
Determine the number of chlorines attached
Eg
. 2 –
chlorobutane
Eg
. 2,2, 3
trichlorohexaneSlide9
Alcohols
The alcohol in alcoholic drinks is ethanol and is just one of many alcohols
Methanol, ethanol,
propanol
,
Butanol
etc. All exist and are named according to the number of carbons in the parent chain
One thing all alcohols have in common is their functional group which gives them their characteristic properties
This is the Hydroxyl group (OH)Slide10Slide11Slide12
Remember
Each carbon atom is basically tetrahedral shaped but the carbon with the OH group attached is v-shapedSlide13Slide14Slide15Slide16Slide17Slide18Slide19Slide20Slide21Slide22Slide23Slide24Slide25Slide26Slide27Slide28Slide29Slide30Slide31Slide32Slide33Slide34Slide35Slide36Slide37Slide38
10cm
3
4cm
3
12g
10cm
3Slide39
Preparation of ethanal
The first test tube should be discarded.
Add small amounts of calcium carbide as it is very reactive with water
Slide40
Preparation of ethanal
Why is it necessary to turn off the Bunsen burner or heating element before the reaction is started?
The reaction would become too vigorous, and some unreacted ethanol and other material is likely to be forced over into the conical flask. Once the mixture in the reaction vessel has been brought to the boil, further heating is not required as the oxidation of ethanol is an exothermic reaction, and gentle boiling can be maintained by regulating the flow from the dropping funnel.Slide41Slide42
Ketones
Functional group of
ketones
is C-C=O
C
The only structural difference between
aldehydes
and
ketones
is that hydrogen atom in
ketones
is replaced by an alkyl group
Rememeber
Ald
H
ydes
have the H the Hydrogen
Because the carbonyl group has two alkyl groups attached it can never be at the end of the chain
There are only two
ketones
on your courseSlide43Slide44
Properties of ketones
Higher boiling points than corresponding
alkanes
(due to presence of dipole-dipole forces)
Boiling points are lower than those of corresponding alcohols due to lack of hydrogen bonding
The polarity of the carbonyl group in
lower members
of the
ketones
causes them to be very soluble in waterSlide45Slide46Slide47Slide48Slide49Slide50Slide51
Preparation of ethanoic acid
Reflux (20 mins)
5g of sodium dichromate
5cm
3
of sulphuric acid
Cool flask with tap waterSlide52
Preparation of ethanoic acid
Mix 2 cm3 of ethanol and 10 cm3 of deionised water in the dropping funnel.
2.Add the solution from the dropping funnel
dropwise
down the condenser, while swirling the contents of the flask and cooling it if necessary to prevent too vigorous a reaction.Slide53
Cool the apparatus, dismantle and rearrange for distillation
Slide54
Preparation of ethanoic acid
Round flask used instead of pear shapedSlide55
Precautions
Reflux distillation involves condensing the vapour from a boiling liquid in such a way as to return the condensed material to the reaction vessel.
In this way a reaction may be carried out at quite a high temperature while preventing the loss of any of the reactants or products. Slide56Slide57Slide58Slide59Slide60Slide61Slide62Slide63Slide64Slide65
EstersSlide66
Esters are prepared in lab by the reaction between an
alcohol
and a
carboxylic
acid Slide67
The lower members of the ester family are volatile liquids with pleasant fruit smells.They give scent to fruit
and flowersSlide68
Uses of organic acids
Esters are used as artificial perfumes or scents as they emit a sweet smell.
Esters are used in making artificial food flavours that are added in many edible items like ice creams, soft drinks, sweets, etc.
Esters are used as industrial solvents for making cellulose, fats, paints and varnishes.
Esters are used as solvents in pharmaceutical industries.
Esters are used as softeners in plastic industries and molding industries
Slide69Slide70Slide71Slide72Slide73Slide74Slide75Slide76Slide77
3 fatty acids and glycerolSlide78
Practical set up
Reflux
DistillationSlide79
SaponificationSlide80
SoapSlide81
Aromatic CmpoundsSlide82
Aromatic compounds are compounds that contain a benzene ring structure in their molecules
Benzene is planar
Benzene is non polar as there is a small
electronegativity
difference between hydrogen and carbon
It was traditionally used as a solvent but was found to be carcinogenic so methyl benzene (toluene is now used instead)
Would you predict it would be soluble in water or
cyclohexane
?Slide83
Organic Natural productsSlide84
Many organic compounds are found in nature and are referred to as “natural products”
Examples include caffeine,
benzaldehyde
(in almonds)
, nicotine, quinine and limonene
19
th
century mainly concerned with finding ways to isolate useful compounds such as morphine
Now it is possible to work out the molecular structures and synthesize these in the laboratorySlide85
Steam distillation
This is a method of extracting oils from plants
It involves distillation in a current of steam
It is very important to avoid too high a temperature as the oil may become damaged
If the oil and water separate naturally they can be isolated using a tap funnel
If an emulsion is obtained (where the oil drops are dispersed throughout the water) then an organic solvent that will dissolve the oil but not the water needs to be usedSlide86
The organic solvent can be separated from the water with a tap funnel
The organic solvent may then be evaporated and a pure sample of the
oil remains