Alcohols II

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Overview:

Alcohols II continues the study of this class of compounds and includes an extensive list of alcohol reactions and analysis. A section addressing balancing organic oxidation-reduction reaction is included. Alcohols are introduced as lead players in the role of synthesis development.

The reactions addressed in this unit include dehydration, substitution, alkoxide formation, oxidation, reduction, esterification, tosylation, and the Pinacol rearrangement. In the section on dehydration, the use of phosphoryl chloride is introduced and the way in which dehydration using that reagent differes from dehydration with sulfuric acid is noted. Just as the mechanism for dehydration with sulfuric acid was addressed in a prior unit, the mechanism for dehydration using phosphoryl chloride is detailed, here. Substiution vs. Elimination is constantly reviewed.

Again, the order of oxidation/reduction of organic compounds is reviewed and stressed as an aid to learning the oxidation products forming and being formed by alcohols. Comparison of first, second, and third degree alcohols and their oxidation products are made. The use of pyridinium chlorochromate as a substitute for the hot copper wire is introduced as an easy method for oxidizing alcohols to aldehydes rather than acids. The commonly expected oxidizing agents such as potassium permanganate, sodium dichromate in both acid and base, as well as the Jones reagent, etc. are used. Esterification without mechanism is discussed for both reactions of alcohols with organic and inorganic acids. Again, patterns of reactions are stressed, as well as usage in such fields as biology and biochemistry. A similar reaction, tosylation using tosyl chloride, is presented and compared as an esterification process. The mechanism for esterification is presented in detail in a later unit entitled Derivatives of Carboxylic Acids. At that point, the two different mechanisms are developed, beginning with Fisher esterification of first, second, and third degree alcohols.

The Pinacol rearrangement is an elegant process that brings together many aspects of reactions regarding alcohols. The mechanism and stabilizing structures are presented in this section.

All too often, organic students need to be able to balance organic reactions but become lost when they attempt to determine the oxidation number of the various atoms involved. Although it is common to write the unbalanced equation with reagents or catalysts placed over and under the arrows, such does not lend itself to producing an equation suitable for sometimes-required calculations. The Chemistry Professor has developed a section to address a straight-forward method of balancing these oxidation-reduction reactions of organic chemistry, and it is presented at the end of this unit.

 

 

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