synthesis of alkenes

Topics: Hydrogen, Alcohol, Redox Pages: 3 (902 words) Published: April 9, 2014
Abstract:
The purpose of this laboratory is to convert benzophenone to diphenylmethanol. This was done by using sodium borohydride to reduce benzophenone. The product was then crystalized from hexanes then using the melting point and IR testing it was possible to characterize it. The melting point range was… Introduction:

This lab is possible because of oxidation and reduction reactions. In organic chemistry oxidation is the loss of electron density around a carbon, while reduction is an increase in electron density around a carbon. More electronegative atoms such chlorine have a strong affinity for electrons while conversely low electronegative atoms have a low affinity for electrons. This unequal affinity for electrons causes an unequal distribution of electrons in a molecule. The unequal distributions causes dipoles or a negative charge around the electronegative atoms and a positive charge around the non-electronegative. An example of such a reaction is:

Figure 1

An example of a reduction reaction is:
Figure 2

A catalytic hydrogenation reductions are a specific type of reduction reaction that require high temperature and pressure along with a metal catalyst and H2. A major short coming of this sort of reduction is that it is non-selective, therefore it will break every Pi bond in a molecule. This limits its use for synthesis reactions. An example of such a reaction is: Figure 4

The type of reduction used in this lab is a nucleophilic hydride reduction. Nucleophilic hydride is unstable by itself so it must be used through a hydride reagent such a NaBH4 or LiAlH4. The hydrogen is more electronegative than boron and aluminum giving it a negative charge. This causes the hydrogen to act like a hydride. This is important because it causes it causes it to be selective. A hydride has a negative charge so it will attack the positive carbon in a carbonyl group. This makes it more useful in synthesis reactions because if a molecule has a carbonyl...


References: 1. “MSDS.” Science Lab.Com Chemicals and Laboratory Equipment. 2005. Web. 24 Mar. 2014 http://www.sciencelab.com/msdsList.php
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