Download organic chemistry - Turner Fenton Secondary School

ORGANIC CHEMISTRY
Once again the maximum bonds that can be made with carbon are four to
satisfy octet. The bond angles between any two carbons in an alkane chain
is 109.5, this is also true of methane. There exceptions of course, for
example, cyclical structures have different bond angles.
ALKYL Groups continued:
Isopropyl –
sec-butyl –
iso-butyl –
tert-butyl
Nomenclature of Hydrocarbons Involving Halides
Halides = Halogens = F, Cl, Br, I
 The nomenclature of naming hydrocarbons with Halides on them remains
the same as naming a hydrocarbon containing an alkyl group. However,
instead of Fluorine ethane it is Fluoroethane for example. Therefore
change the -ine ending to –o for each halogen.
 What if there are two different halogens present on the same
hydrocarbon? Then is there priority? No…just alpha order. But
halogens get priority over alkyl groups.
Cl
Br
Other examples: Draw the structure of mothballs: para-dichlorobenzene
Aromatic Compounds are derivative of benzene
Facts about Benzene
 First isolated by Michael Faraday, 1825
 Colourless, sweetish-smelling liquid
 August Kekule proposed a ring structure with alternating single and
double bonds. (1864)
 It is a planar molecule (flat)
 Studies show that the bond length are all the same: 139pm. (the bond
length of C-C bond is 148pm while a C=C is 134pm)
Naming benzene compounds:
When benzene is represented as a branch that it is named: PHENYL
When a benzene ring has substituents around it, then the normal method of
naming a cyclical hydrocarbon is used. Numbering of the six carbon atoms
is done such that the alkyl groups or other substituents have the lowest
possible number.
The two-Branches on a benzene deal:
 Chemists use a different method of naming benzene instead of using
position numbers. The prefixes used are: ORTHO, META and PARA.
ALCOHOL is coming up next …. No we are not going to drink!!
Organic functional groups may bond with a carbon of an aliphatic compound
to produce a compound with a new name but more importantly with physical
and chemical properties that are unique to the functional group.
ALCOHOL NOMENCLATURE
Alcohols are compounds that contain the functional group –OH (Hydroxyl
group). This hydroxyl group can be attached to one, or two or even three
alkyl groups. The short way of representing an alkyl group is using R.
Therefore: an alcohol can generally be represented at R-OH
 Recall: the presence of an OH group means that Hydrogen bonding is
possible.
 Isomers are possible with alcohols containing more than 2 carbon
atoms.
What about priority of position numbers in a chain with different types of
branch groups? Yes this is important. The priority is as follows:
-OH > -F, -Cl, -Br, -I
> -R groups
Naming:
1. Find longest chain containing the –OH group and name the parent chain
(look for double bonds etc for ending of hydrocarbon).
2. Change ending to –ol. For example CH3OH is named Methanol. If there
is a double/triple bond involved then the Hydroxyl group gets priority.
3. If more than one hydroxyl group present then leave parent chain as it.
Use prefix to represent number of OH present (di, tri, tetra etc) and add
the –ol suffix.
For example: CH3CH2OH
C(CH3)3OH
Draw the structures for the following:
a) Ethylene glycol (1,2-ethanediol)
b) 1-chloro-3,3-dimethyl-2-butanol
Alcohols are classified according to the type of carbon atom bonded to the
hydroxyl group:
Primary Alcohol: RCH2-OH
Secondary Alcohol: RR`CH-OH
Tertiary Alcohol: RR`R”C-OH
Note: R, R` and R” represents alkyl groups attached to carbon which in turn
is bonded to the hydroxyl group.
Aside: benzene attached to a single hydroxyl group is called a Phenol.
Hmm…Why do I feel so sleepy? Do I smell an ether!
ETHERS – The alkoxy alkane method
Two hydrocarbons connected by an “O” (oxygen) and thus ether compounds
have the formula R-O-R`. Mostly used for solvents in organic reactions
Naming:
1. Larger R group is the parent chain. Name it as usual.
2. Smaller R group is the prefix but ending is alkOXY.
3. Write the alkoxy group followed by parent chain name.
Examples:
CH3CH2CH2OCH2CH3
CH3CH2CH2OCH(CH3)CH2CH3
So far we have considered single bonds between carbon and oxygen. Now,
we will consider the naming of hydrocarbon compounds containing double
bonds between carbon and oxygen (C=O).
ALDEHYDES
The aldehyde functional group can be represented by R-HC=O or R-CHO.
This always appears at the end of a hydrocarbon chain. This makes the
naming of an aldehyde simple.
Naming: Remove the “e” ending of an alkane and replace with –al.
Example: CH3CHO
CH3CH2CHCH-CHO
Draw the following: 4-bromo-3-methylheptanal and 3-hydroxybutanal.