propanol

Propanol is an alcohol with 3 carbon atoms. It comes in 2 isomers as illustrated below:

     H   H   H                H   OH  H
 H - C - C - C - OH       H - C - C - C - H
     H   H   H                H   H   H
   1-propanol              2-propanol or
                           isopropyl alcohol

Some physical data for 1-propanol:

• Melting point:-127 C
• Boiling point:97 C
• Density:0.804 g/mL at 25 C

Some physical data for 2-propanol:

• Melting point:-90 C
• Boiling point:82 C
• Density:0.786 g/mL at 25 C
• Dielectric constant:18 Debye at 25 C

Uses of 2-propanol include: acting as a cleaning agent; disinfectant; acting as a solvent for oils and inks; as a reagent in synthesis of other commercial chemicals. It is used as a rubbing ointment as well.

Synthesis of 1-propanol is performed by use of Grignard reagents. The use of organomagnesium halides, Grignard reagents, was developed early in the 20th century by the French chemist Victor Grignard, who for that reason shared the Nobel prize for chemistry in 1912. The Grignard reaction has proved to be one of the most versatile methods for the formation of carbon-carbon bonds. Addition of Grignard reagents to aldehydes leads to primary or secondary alcohols whereas addition to ketones provides tertiary alcohols. Additions to carbonyls by Grignard reagents are reduction reactions.

In a typical Grignard reaction the organohalogen compound is slowly added to magnesium metal suspended in an ether solvent. There is usually a short wait until reaction begins, and then the mixture becomes cloudy as the exothermic reaction proceeds. The Grignard reagent is normally not isolated but is utilized immediately by slowly adding to it an ether solution of the carbonyl compound. To this point all reagents must be anhydrous because Grignard reagents react rapidly with water. After reaction between the Grignard reagent and the carbonyl compound is completed, dilute aqueous acid is added to product the alcohol product.

The reaction is: CH₃CH₂MgBr + HCHO -> CH₃CH₂CH₂OH

Synthesis of 2-propanol is achieved by adding water to propylene under acidic conditions due to Markovnikov orientation. This method has been developed industrially in very important large-scale processes. Isopropyl alcohol synthesis by hydration of the readily available alkene propylene is an imporant product of the petrochemical industry as are Ethyl, sec-butyl and tert-butyl alcohols which are made using the same principle.

The reaction is:CH₃CH=CH₂ + H₂O -> CH₃CH(OH)CH₃