Grigard Lab

Grigard Lab - Grignard Reaction November 10, 2011 Purpose:...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Grignard Reaction November 10, 2011 Purpose: The purpose of this experiment was to synthesize the tertiary alcohol triphenylmethanol from a Grignard reagent, phenyl magnesium bromide. The Grignard reagent was synthesized from bromobenzene and magnesium and then reacted with benzophenone to produce triphenylmethanol. It was important that water be excluded from the reaction, in order to prevent the formation of benzene. The reaction of phenyl magnesium bromide and benzophenone was quenched with sulfuric acid, and an extraction was performed in order to separate the organic phase containing the triphenylmethanol from the aqueous phase. The triphenlmethanol was then isolated and purified by crystallization and vacuum filtration. Once that is done we have to do the melting point, TLC and IR Spectrum to verify the purity of the compound. Introduction: Carbon-carbon bonds are the basis of organic chemistry. Attaching carbons and other organic molecules together we can create new molecules and carry out even more reactions to further manipulate our product. In 1912 F.A. Victor Grignard won the Nobel Prize for his discovery of a new reagent, a “rignard Reagent” used in such a reaction, coined “Grignard Reaction”. The Grignard Reagent is made up of organomagnesium, an organometallic molecule, or a molecule with both an organic and metal component. These reagents differ by the character of the carbon-metal bond and can be categorized as ionic, polar covalent, and covalent. The difference in electronegativity between the metal and carbon atoms makes ionic organometallic reagents highly reactive. These substantial differences in electronegativity induce a separation of charge where the electrons are not evenly distributes over the entire molecule. As a result, these compounds can be difficult to control. Examples include NaCH3 and KCH2CH2CH3. The metals in both of these compounds have an oxidation of +1, which puts leaves a positive charge on the metal and a negative charge on the organic group. This makes the molecule even more unstable because typically these organic groups do not like a negative charge. Polar covalent organometallic reagents contain a covalent bond between the carbon atom and the metal. These compounds are also highly reactive and, however the differences in electronegativity are not as great as ionic reagents. As a result they are much easier to control. An example of a polar covalent organometallic reagent is n-butyl lithium. This popular reagent has strong bacidity and is nucleophillic. As the name suggests, Covalent organometallic reagents have a completely covalent bond between the carbon atom and the metal. In this case, there is only a small difference in the respective electronegativities and there is little charge separation. Thus, these compounds are relatively stable and non-reactive, they are rarely used in Griignard reactions. Typical Grignard Reactions use the polar covalent organometallic reagent with a moderate
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 11/16/2011 for the course CHEM 245 taught by Professor Burdette during the Spring '08 term at UConn.

Page1 / 8

Grigard Lab - Grignard Reaction November 10, 2011 Purpose:...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online