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Alcohols


There are various groups of atoms, called functional groups, that give organic compounds characteristic properties. One is the functional group -OH (called the hydroxy group). In naming and organizing many organic compounds, including alcohols, it is convenient to consider them as functional groups attached to a hydrocarbon unit. The hydroxyl group in an alcohol does not function the same way as the OH'- polyatomic ion in other inorganic compounds. That is, alcohols do not dissociate to form hydroxide ions in water solutions.

Alcohols:

1) methanol
(methyl alcohol) b.p. 65 °C , m.p. -98 °C H
density 0.793 g/cm3, soluble in water
uses: fuel, solvent, to prepare other compounds 
prepared: destructive distillation of wood
(common name: WOOD ALCOHOL) but now done chemically 
danger: extremely poisonous when swallowed, attacks nervous system and optic nerve (blindness/death)

        H
         |
 H -- C --OH
         |
        H


2) ethanol
(ethyl alcohol) b.p. 78.5 ° C, m.p. -117 ° C
density 0.789 g/cm3, soluble in water 
uses: solvent, fuel, preparations, germicide,
alcoholic beverages (known as GRAIN ALCOHOL because it is prepared from corn and grain plants.)
DENATURED: rendered unfit to drink by adding methanol. 

 

          H    H
       |     |
H --C -- C -- OH
      |      |
      H     H


3) 2-propanol 
(isopropyl) b.p. 82 °C 
known as common rubbing alcohol

 

       H    OH   H
        |      |     |
  H - C -- C -- C -- H
        |      |     |
       H     H    H


4) 1-propanol 
b.p. 97 °C

        H   H   H
         |    |    |
 H -- C --C -- C -- OH
         |    |     |
        H    H    H

 


5) ethylene glycol 
known as antifreeze ingredient

    H   H
    |    |
H-C --C- H
    |    |
  OH  OH

 


6) glycerine
viscous, clear liquid obtained as by product in soap
making, used to make plastics, drugs, foods, cosmetics, H I
and nitroglycerine

    OH  OH   OH
      |     |      |
H --C -- C -- C -- H
      |     |      |
     H     H    H

 

Name chemical formula boiling point # atoms/mlcl
methyl alcohol CH30H 66° C  
ethyl alcohol C2H50H  78° C  
propyl alcohol C3H7OH  97° C  
isopropyl alcohol C3H7OH  83° C  
butyl alcohol  C4H90H 117° C  
amyl (pentanol)      
hexyl alcohol      



Questions

 1) Fill in the rest of the chart.

2) What is the relationship between the boiling point of the alcohol and the number of atoms in its molecule?

3) What is a possible reason for the difference in boiling points of propyl and isopropyl alcohol.

4) How could you separate a mixture of methyl and butyl alcohol?

5) How can a sample of ethyl alcohol be rendered unsafe to drink?

6) Describe the nature of an alcohol burning.

7) Is there any pattern evident concerning the density of different alcohols?

8) Draw the chemical formulas for all acids studied.


 

Page Last Updated: Friday March 02, 2007           Webmaster: Larry Jones                 Pickens County School District