Alcohols
The most important example is ethanol
sum formula
C2H6O better: C2H5OH
Lewis formula
skeletal formula
group formula
CH3CH2OH
structural formula
Formation of Ethanol
1. By fermentation:
2. Technical:
C6H12O6 -------------------> ...... CO2 + ......... C2H5OH
by the addition of water to ethene
Usage of ethanol
Drinks, spot removers, for disinfection, as a solvent (in perfumes; in the industry), methylated spirit;
ethanol as a fuel: Problem: big cultivation areas are necessary. in Brazil 1/4 of all cars.
Further alcohols
Beside ethanol there are some more alcohols. Alcohols belong to a compound class whose best known
representative is ethanol.
The other alcohols also contain the typical OH-group which is bound to a hydrocarbon framework (an
organic rest).
H
H
H
C
C
O
H
H
H
Ethyl residue
Hydroxy group
O
R
H
R: general organic residue
Organic residues which are derived from alkanes are designated alkyl
residues.
Nomenclature of alcohols: Name of the suitable alkane + suffix "ol"
Properties of related alcohols
Methanol
Alcohol
Ethanol
1-Propanol
1-Butanol
Skeletalformula
Lewisformula
-------- becomes smaller / bigger ----------->
The alkyl residue
The solubility in water (hydrophily) --------- increases / decreases ------------>
The solubility in heptane (lipophily) --------- increases / decreases --------------->
The boiling point: ------------ becomes higher / lower ------------------------------------>
Which alcohol has the higher boiling point?
OH
Bp. 83°Coder
Bp. 138°C
OH
OH
OH
Bp. 97°C
or
HO
OH
Bp. 290°C
Isomeric alcohols with the example of the isomeres of butanol
Lewis formula
Name
General designation
Butanol
primary Alcohol
R
The C-atom which carries
the OH is primary (one
Alkyl residue is bound to H
it)
OH
OH
2-Methyl-propanol
OH
2-Butanol
OH
2-Methyl-2propanol
tert. Butanol
General 3-dimensional
designation
OH
H
"
"
secondary Alcohol
2 alkyl residues on the
OH-carrying C-Atom
(secondary C)
R1
tertiary alcohol
3 alkyl residues on the
OH-carrying C-Atom
(tertiary C)
R1
R2
R2
OH
H
OH
R3
Examples of known alcohols
Methanol
a colourless liquid; tastes almost like ethanol;
Boiling point (B.p.): 65°C
20 to 50 ml are deadly; 5 to 10 ml lead to loss of sight and brain damage.
Formation:
with the "dry distillation" of wood (old name: "wood alcohol"); moreover, by the improper
accomplishment of the distillation and use of inapt basic material;
technically: CO + 2 H2----> CH3OH
Use:
Solvent and raw material for the chemical industry; as a fuel (only in the project phase)
Propanol, Butanol and Pentanol originate as undesirable by-products of the alcoholic
fermentation and are included in small quantities in all alcoholic beverages. They are more toxic than
ethanol and amplify the hangover effect (after too plentiful consumption of alcohol) substantially .
Isopropanol (2-Propanol)
B.p. 82°C
Skeletal formula:
important solvent: Many glasses- and screen-cleaners are
practically pure 2-propanol which is sold terribly expensively.
It loosens glue very well, however without loosening plastics which is the case with acetone.
Ethylene glycol (1,2-Ethandiol)
a bivalent alcohol
Skeletal formula:
a toxic, sweetly tasting liquid (from Greek glycos = sweet;
the more OH-groups, the sweeter);
B.p. 198°C
Use:
as a raw material for the plastic production
as an antifreeze in the car (engine cooling, windshield wiper); a 1:1 mixture from ethylene glycol and water
freezes only at -40°C.
Glycerol (1,2,3-Propantriol)
B.p. 290°C
a trivalent alcohol
Skeletal formula:
a sweetly tasting, viscous liquid; completely indissolvable in pentane ;
very well water-soluble; takes up if even air humidity (is hygroscopic - water attracting);
can form several H-bonds - thereby it becomes viscous;
Use:
to hold creams, toothpastes and stamp colours damp
Component of fats (see later);
for the production of nitroglycerine
(correct name: Glycerol trinitrate):
Nitrogycerine is a colourless oily liquid. Dynamite is N. soaked up in porous kieselguhr.
With sudden heating or with vibration or impact a violent explosion occurs:
4 C3H5(NO3)3
--------> … CO2 + … H2O + ….N2 + O2