Question: Draw the mechanism of the reaction you will complete in lab. Use the proper arrow drawing convention to show all bond making and bond breaking steps in the reaction.
Classes Of Functional Groups
Organic Chemistry deals mostly with carbon and hydrogens, also called hydrocarbons, but those groups which replace hydrogen and bonds with carbon to give a characteristic nature, unique of their own, to the hydrocarbon they are attached to, are called functional groups. All the compounds belonging to a functional group undergo reactions in a similar pattern and are known to have similar physical and chemical properties.
Characteristics Of Functional Groups
In organic chemistry, we encounter a number of special substituent groups which are attached to the hydrocarbon backbone. These groups impart certain characteristics to the molecule of which it is a part of and thus, become the highlight of that particular molecule.
IUPAC Nomenclature
In Chemistry, IUPAC stands for International Union of Pure and Applied Chemistry which suggested a systematic naming approach for the organic and inorganic compounds, as in the beginning stage of nomenclature one single chemical compound was named in many ways by which lead to confusion. The need for this approach aroused as the number of chemical compounds newly discovered were increasing (approximately 32 million compounds) and the basic concept of nomenclature i.e. the trivial nomenclature and the derived system of nomenclature failed to overcome the challenge. It is an important task to name a chemical compound systematically and unambiguously which reduces lots of confusion about the newly reported compounds.
Question: Draw the mechanism of the reaction you will complete in lab. Use the proper arrow drawing
convention to show all bond making and bond breaking steps in the reaction.
Background info:
A substitution reaction takes place when a nucleophile (Nu:) forms a bond with a carbon
atom, displacing a leaving group (L).
SN2 reaction
Leaving groups are typically weak Bronsted bases that are stable as anions (often halide anions).
The precise timing of when the leaving group leaves depends on the structure of the substrate –
the molecule bearing the leaving group. Methyl and primary
type reactions. In this type of reaction, the nucleophile attacks the carbon from the side opposite
the leaving group and the nucleophile-carbon bond is made simultaneous with the carbon-leaving
group bond breaking. SN2 reactions are one-step and there is an inversion of stereochemistry at
the carbon bonded to the nucleophile.
SN1 reaction
If the carbon undergoing substitution is sterically hindered (as is the case with tertiary alkyl
systems) or the intermediate carbocation is relatively stable (tertiary alkyl or resonance
stabilized systems), SN1 reactions are prevalent. In this case, the nucleophile cannot approach
the carbon bearing the leaving group as it would in an SN2 reaction or the carbocation is fairly
stable, and the leaving group leaves first, forming a planar carbocation with a formal positive
charge on the carbon. Once the carbocation is formed, it is attacked by the nucleophile forming a
new bond. Reactivity, in terms of SN1 substitutions, is based on the stability of the carbocation
intermediate formed. SN1 reactions are two step reactions where the first step involves the
formation of the carbocation and the second step involves the attack of the nucleophile. Because
of the achiral nature of the carbocation intermediate, if the carbon bearing the leaving group is
chiral, then stereochemistry is lost in an SN1 reaction.
The reaction you will be carrying out in lab will convert 9-fluorenol to 9-methoxy fluorene using
a nucleophilic substitution reaction.
up a reflux apparatus using a 10 mL round-bottom flask and a water condenser (which can be
found in the red kit on your bench).
Before attaching the round bottom flask, add your spin
bar and 200 mg of 9- fluorenol (pre-weighed) to this flask
and place it in your cork ring for safe holding. Measure
out approximately 6 mL of methanol into your graduated
cylinder. In the hood, slowly add 1.5 mL of concentrated
sulfuric acid to the methanol with a transfer pipette
(CAUTION: concentrated sulfuric acid is a strong acid.
In case of contact with ANY organic material,
immediately wash with cold water. Do not leave ‘drops’
of sulfuric acid on the table. Dispose of the transfer
pipette in the container in the back of the hood.). The
solution will become hot as the sulfuric acid is added
(Why?). Return to your bench and pour the
H2SO4/MeOH mixture into your flask and reassemble
your reflux apparatus. Rinse the graduated cylinder with
cold water. Start circulating the water in the water
condenser. The water flow should be a slow steady
stream and should enter from the bottom of the
condenser.
Set the reaction flask in the largest hole in the aluminum block and set the thermometer in the
smallest hole of the aluminum block using the thermometer clamp. Heat the reaction mixture to
about 100ºC while stirring. The solution should boil gently. Heat the solution for a total of 20
minutes, beginning from the time the reaction flask is put on heat. Remove the reaction flask
from heat, i.e. unplug and move your hot plate, and allow it to cool to approximately room
temperature, but do not detach the flask from the condenser yet. Be careful not to shake the
flask when removing it from the heating block because it may start to boil violently.
During this time obtain two spotting pipettes. Put a small amount of 9-fluorenol in a
disposable culture tube and add enough dichloromethane to dissolve the sample.
Once your reaction has cooled, prepare a TLC plate and spot it with 9-fluorenol and your
UV light and trace around the spots. Pour your reaction mixture into the waste bottle
provided in the hood.
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