Sodium Borohydride Reduction of 9-Fluorenone.
IR Analysis of Product
November 29, 2007
Methods and Background
The purpose of the lab is to produce a ketone, 9-fluorenone, and reduce it to an
alcohol, 9-fluorenol, using sodium borohydride.
The identity of the product was then
supposed to be verified through the use of an IR spectroscopy and melting point
In this lab, the process of reduction is observed.
This process is a basic chemical
reaction that can be defined as the gain of electrons.
In organic chemistry, however, it
does not involve a gain of electrons, but instead an increase in electron density at a
carbon atom due to a replacement of bonds to more electronegative atoms, the gain of
bonds to hydrogen, or a decrease in oxidation number.
Organic functional groups that
contain double and triple bonds go through a reduction process when there is a net
addition of elements of one or two molecules of hydrogen across the π-bond, thus causing
unsaturated compounds to become saturated because they can no longer accept any
Reduction are effected by either catalytic or chemical methods.
method, catalytic hydrogenation, involves the addition of a molecule of hydrogen across
a carbon-carbon or carbon double or triple bond in the presence of a metal catalyst.
chemical reduction of many organic functional groups is effected by using a metal
hydride as a reducing agent.
Metal hydride reducing agents have different reactivities
toward distinct functional groups.
This is important because of the fact that these
reducing agents react selectively with only one type of functional group.
lithium aluminum hydride is very reactive and unselective, that reduces aldehydes,
ketones, carboxylic acids, esters, and amides.
Sodium borohydride, on the other hand, is
less reactive and more selective, reducing only aldehydes and ketones to primary and
secondary alcohols, respectively.
The experiment calls for the reduction a carbonyl group to alcohol by catalytic
hydrogenation or with metal hydrides.
In this lab, it involves the transfer of a hydride ion
from a borohydride ion to the electrophilic carbonyl carbon of 9-fluorenone, while the
boron atom transfers to the carbonyl oxygen.
When this happens, all 4 hydrogen atoms
attached to the boron get transferred along with it to produce the intermediate borate salt.
When this undergoes hydrolysis in acidic conditions, it decomposes to form the wanted