Sodium Borohydride Reduction: Diphenylmethanol from Benzophenone
Megan Entwistle, Maria Amos, and Paul Golubic
CHEM 0330 Organic Lab 1
Sodium Borohydride Reduction: Diphenylmethanol from Benzophenone
11/16/11
Introduction
Redox (shorthand for REDuction-OXidation) reactions are chemical reactions in which the oxidation state (or oxidation number) of atoms has changed. Oxidation can be observed through the loss of electrons or an increase in oxidation state by an atom, ion or molecule. Reduction describes the gain of electrons or decrease in oxidation state of an atom, ion or molecule. However, there are many processes that are classed as redox even though no electron transfer occurs, for example those reactions that involves covalent bonds.
Reduction reactions can be determined through three features. The first is a loss of oxygen from a bond or loss of a bond to oxygen as in the case of carbon-oxygen double bond to a carbon-oxygen single bond. The second is the addition of hydrogen to a bond and thirdly, the replacement of a more electronegative atom with carbon or hydrogen.
In redox reactions, the reductant (or reducing agent) loses electrons and is oxidized while the oxidant (or oxidizing agent) gains electrons and is reduced. The reducing agent transfers electrons to another substance. The agent reduces other substances and so, the agent itself is oxidized. The reductant is also called an electron donor as it donates electrons. The electron donors can also form charge transfer complexes with electron acceptors. Examples of good reducing agents are electropositive metal elements such as lithium, sodium, iron, aluminium, zinc, iron, magnesium and carbon. These metals donate electrons readily. In organic chemistry, there are very diverse reductants. For example, in a catalytic reduction to reduce carbon-carbon double or triple bonds, the main reductant would be hydrogen gas (H2) coupled with Lindlar’s catalysts (palladium, platinum or nickel). Hydrogenation reduces most types of multiple bonds. Another method of
CHEM 0330 Organic Lab 1
Sodium Borohydride Reduction: Diphenylmethanol from Benzophenone
11/16/11
Introduction
Redox (shorthand for REDuction-OXidation) reactions are chemical reactions in which the oxidation state (or oxidation number) of atoms has changed. Oxidation can be observed through the loss of electrons or an increase in oxidation state by an atom, ion or molecule. Reduction describes the gain of electrons or decrease in oxidation state of an atom, ion or molecule. However, there are many processes that are classed as redox even though no electron transfer occurs, for example those reactions that involves covalent bonds.
Reduction reactions can be determined through three features. The first is a loss of oxygen from a bond or loss of a bond to oxygen as in the case of carbon-oxygen double bond to a carbon-oxygen single bond. The second is the addition of hydrogen to a bond and thirdly, the replacement of a more electronegative atom with carbon or hydrogen.
In redox reactions, the reductant (or reducing agent) loses electrons and is oxidized while the oxidant (or oxidizing agent) gains electrons and is reduced. The reducing agent transfers electrons to another substance. The agent reduces other substances and so, the agent itself is oxidized. The reductant is also called an electron donor as it donates electrons. The electron donors can also form charge transfer complexes with electron acceptors. Examples of good reducing agents are electropositive metal elements such as lithium, sodium, iron, aluminium, zinc, iron, magnesium and carbon. These metals donate electrons readily. In organic chemistry, there are very diverse reductants. For example, in a catalytic reduction to reduce carbon-carbon double or triple bonds, the main reductant would be hydrogen gas (H2) coupled with Lindlar’s catalysts (palladium, platinum or nickel). Hydrogenation reduces most types of multiple bonds. Another method of
References: "Carbonyl Reactivity." Michigan State University :: Department of Chemistry. Web. 13. Nov. 2011 Computers in Chemical Education (CCE) Newsletter. Web. 13 Nov. 2011. <http://orgchem.colorado.edu/CCCE/frame/images/handbook.pdf>. Organic Chemistry I Laboratory Manual. Plymouth: Hayden-McNeil, 2012. 92. Print. [ 3 ]. "Stereospecific Reduction of Benzil with Sodium Borohydride; Determination of the Stereochemistry by NMR Spectroscopy." Web. 13 Nov. 2011. . [ 4 ]. Padias, Anne B. Making the Connections²: A How-To Guide for Organic Chemistry Lab Techniques. 2nd ed. Plymouth, MI: Hayden McNeil, 2011. Print. [ 5 ]. "The Organic Chemistry Laboratory Web Pages - UW Madison." Home | UW Madison - Department of Chemistry. Web. 13 Nov. 2011. . [ 6 ]. Computers in Chemical Education (CCE) Newsletter. Web. 13 Nov. 2011. . [ 7 ]. Huston, Erica. "Sodium Borohydride Reduction: Diphenylmethanol from Benzophenone." Organic Chemistry I Laboratory Manual. Plymouth: Hayden- McNeil, 2012