Chemoselective, Syntheses of Natural Fragrance and Perfume Additives Lab Report
One of the most important concepts within chemistry is the chemoselectivity of
reactions. This concept deals with a how reagent will choose a functional group to react with,
resulting in the formation of the major product. Our lab studied 6 reactions: three oxidation and
three reduction of the three compounds, whose structures are shown below.
Figure 1: Structures of the three starting materials: citral, geraniol, and carvone.
A type of oxidation reactions that was looked at were epoxidation reactions, which
removed a double bond, and replacing it with an oxygen of citral and carvone. Another type of
oxidation reaction is the copper oxidation of geraniol that starts with an already present alcohol
group, which loses its hydrogen and creates a carbon-oxygen double bond. In the reaction carried
out in lab, the alcohol group is attended to a primary carbon, which show a different result. When
the copper bromide reacted with geraniol, the reaction will be like a reaction carried out with
PCC. The reaction schemes for these reactions are shown below:
Figure 2: Reaction schemes for the oxidation of citral, geraniol, and carvone, showing the
reagents and products for each reaction.
In the second week, the three reactions were reduction and hydrogenation reactions. The
first of these reactions was a sodium borohydride reduction of citral, which reduces an aldehyde
or ketone down to an alcohol. A second reduction reaction performed was the Clemmensen like
reduction of carvone, which uses zinc to reduce an aldehyde or ketone to an alkane. Finally, the
last type of reaction was hydrogenation of carvone using a platinum catalyst, reducing any
double bonds. The reaction schemes for these three reduction and hydrogenation reactions are
Figure 3: Reaction schemes for the reduction and hydrogenation reactions carried with carvone
Week One Oxidation Reactions:
Citral and H2O2:
The product of this reaction is formed when NaOH acts as a catalyst, deprotonating the
hydrogen peroxide, and creating an epoxide where the double bond closest to where the aldehyde
was (Cunningham 323). Evidence for this can be found within the IR spectrum of the product
because of the strong peak around 1725 cm-1 that is a C=O stretch, indicative of the aldehyde
group. Also, around 3000 cm-1 that indicate an alkane C-H stretch. The C13-NMR also shows
proof of the aldehyde, with two peaks around 200 ppm.
Copper Oxidation of Geraniol:
The conversion of an alcohol to an aldehyde with the use CuBr is a two-step oxidation
reaction. The IR spectrum of the product shows evidence that the aldehyde was formed because
of the strong peak around 1700 cm-1, which indicated a C=O stretch. Furthermore, a cluster of
peaks around 3000 cm-1 provides evidence for the presence of alkane groups within the product.