Understand the structures, reactions and properties of functional group compounds.
A. D1
Analyse the types of reaction mechanisms undergone by non-carbonyl and carbonyl compounds.
A.M1
Construct mechanisms for non-carbonyl and carbonyl compounds.
A. M2
Plan a multi-step synth...
UNIT 14: APPLICATIONS OF ORGANIC CHEMISTRY
Learning aim, A: understand the structures, reactions and properties of functional group
compounds
Functional groups play a consequential role in the characteristics that the molecules will attain. They
are the replaced atoms or groups that are bonded to certain molecules. The bonded group of atoms
is responsible for the substance’s distinctive chemical reactions they help in determining the
chemical properties of a substance and predict reactions that might occur. They can be also used in
the naming of organic compounds. Carbons and functional groups can bond through covalent bonds,
the atoms of functional groups are bonded together and the rest of the compound by a covalent
bond, and they are classified as:
1, Alpha carbons- first carbon atom attached to the functional group
2, beta carbon- second carbon atom attached to the functional group
3, gamma carbon- third carbon atom attached to the functional group
Halogenoalkanes
In a compound, if one or more hydrogen atom from an alkane is replaced by halogen atoms, they
are called halogenoalkanes. Depending on how the halogen atom is positioned in the chain of
carbon atoms they fall into separate categories.
Primary halogenoalkane (1oC):
Here the carbon carrying the halogen atom is only attached to one other alkyl group. There is one
single exception to this as CH3Br and other methyl halides are sometimes counted as primary
halogenoalkanes despite there being no alkyl groups attached to the carbon that houses the halogen
on it. Here is an example of primary halogenoalkanes
Bromopropane
As seen above Bromine which is a halogen is attached to propane.
Secondary halogenoalkanes (2OC)
Here two carbons are attached to a carbon that is also bonded with a halogen.
2 bromopropane
Here bromine (a halogen) is bonded to a carbon that is also bonded with the other two carbons.
Tertiary halogenoalkane (3OC)
Here the carbon carrying the halogen is bonded with three other carbons (could also be any kind of
alkyl group)
,2- chloro-2-methylpropane
Here the halogen is connected to a carbon that is connected to three other carbons.
Nucleophilic substitution reaction
Halogenoalkanes can be formed when they undergo a reaction called nucleophilic substitution
reaction. This is a chemical reaction between alkenes and hydrogen alkenes. Here a positively
charged electrophile and a nucleophile are reacting. OH- group replaces a halogen atom to give an
alcohol. This reaction makes the discharging group be replaced by an electron-rich compound.
Halogens and carbons have different electronegativities and halogenoalkanes have polar molecules
with a polar C-X bond. The polarity makes an electron-deficient carbon atom, and this carbon atom
of the polar bond attracts nucleophiles. Nucleophilic addition occurs through refluxing with
conditions including sodium/potassium hydroxide, an echoic solvent, and heat.
(CH3)3CBr + NaOH à (CH3)3COH + NaBr (this is a nucleophilic reaction with 2-bromobutane
resulting in alkene propene to be produced)
Below is a drawn mechanism for nucleophilic substitution of 1-iodopropane.
Iodine (halogen) is delta negative because it is electronegative and attracts electrons. But the carbon
is delta positive so the lone pair electrons are attracted to it. This is where the halogen carbon bond
is broken up and leads to the formation of iodine ions.
Elimination
Here the OH- functional group is being replaced by a halogen in alcohol. Atoms are separated into
small groups to form one significant molecule. The halogenoalkanes get heated with ethanol sodium
hydroxide, leading to the breaking of the C-X bond heterolytically, which forms an X- ion and an
alkene are left as an organic product. Elimination in halogenoalkanes is also performed in the form
of refluxing with the presence of sodium/potassium hydroxide and heat.
CH3CHCH3 + NaOH à CH2=CHCH3 + NaBr + H2O
Br
, In the reaction above the hydrogen atom is removed from the carbon by the NaBr. This enables a
double bond to be composed between the carbon atoms by an electron pair. So the bromine ion is
removed and becomes Bromine- (Br-) so the bromine ends up discharging from the group and water
will be formed from the leftover product.
Alcohol
Alcohols are also functional groups categorized by the presence of a hydroxyl function group which
is when one hydrogen and one oxygen atom are bonded together and form -OH. They are organic
compounds that include alcohol groups. Alcohols can give away their hydrogen from the hydroxyl
group because they are acidic naturally (note acids can be Bronsted acid or a base depending on the
other components in the system). The oxygen is given a negative charge when the hydrogen is
released because the O-H bond is polar. Depending on where the functional group is located in the
carbon chain the alcohol can be organized into 3 categories.
Primary alcohol
Here the carbon carrying the -OH group is linked to one alkyl group.
For example, ethanol is a primary alcohol. CH 3-CH2-OH
Methanol (CH3OH) is also considered primary alcohol even though no alkyl groups are attached to
the carbon carrying -OH group.
Secondary alcohols
Here the carbon carrying the -OH group is bonded to two alkyl groups. These alkyl groups can be the
same or different. OH
For example, propan-2-ol (CH3-CH-CH3) is a secondary alcohol.
Tertiary alcohol
Here the carbon carrying the -OH group is bonded to three alkyl groups
OH
For example, 2-methylpropan-2-ol (CH 3-C-CH3) is a tertiary alcohol.
CH 3
Alcohol can be formed using two different processes
1, Fermentation
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