Class 10, Science, Chapter-4, Lecture-6, Alcohols and Acids (Notes)
FUNCTIONAL GROUP:
An atom or a group of atoms in an organic molecule that is responsible for the compound’s characteristic reactions and determines its properties is known as a functional group.
ALCOHOLS:
The compounds of carbon with hydrogen and oxygen which contain hydroxyl (–OH) as principal functional group are called alcohols.
General Formula – CnH2n+1OH
HOMOLOGOUS SERIES OF ALCOHOLS
MOLECULAR FORMULA |
IUPAC NAME |
COMMON NAME |
CH3OH | Methanol | Methyl alcohol |
C3H7OH | Ethanol | Ethyl alcohol |
C4H9OH | Propanol | Propyl alcohol |
C2H5OH | Butanol | Butyl alcohol |
PHYSICAL PROPERTIES OF ETHANOL:
1.Physical State– Colourless liquid
2.Boiling point – 351 K (78 OC)
3.Solubility – Readily soluble in water
CHEMICAL PROPERTIES OF ETHANOL:
1.Combustion:
$$\mathop {{{\rm{C}}_{\rm{2}}}{{\rm{H}}_{\rm{5}}}{\rm{OH}}}\limits_{{\rm{ethanol}}} {\rm{ + 3 }}{{\rm{O}}_{\rm{2}}} \to 2{\rm{ C}}{{\rm{O}}_{\rm{2}}}{\rm{ + }}\mathop {{\rm{3 }}{{\rm{H}}_{\rm{2}}}{\rm{O}}}\limits_{{\rm{water}}} $$
2.Oxidation:
Ethanol oxidises to ethanoic acid when heated with alkaline potassium permanganate or acidified potassium dichromate.
$$\mathop {{{\rm{C}}_{\rm{2}}}{{\rm{H}}_{\rm{5}}}{\rm{OH}}}\limits_{{\rm{ethanol}}} {\rm{ + }}\mathop {{\rm{2 [O]}}}\limits_{{\rm{nascent ~oxygen}}} \mathrel{\mathop{\kern0pt\longrightarrow}
\limits_{{\rm{Heat}}}^{{\rm{Alkaline KMn}}{{\rm{O}}_{\rm{4}}}}} \mathop {{\rm{C}}{{\rm{H}}_{\rm{3}}}{\rm{COOH}}}\limits_{{\rm{ethanoic ~acid}}} {\rm{ + }}\mathop {{{\rm{H}}_{\rm{2}}}{\rm{O}}}\limits_{{\rm{water}}} $$
$$\mathop {{{\rm{C}}_{\rm{2}}}{{\rm{H}}_{\rm{5}}}{\rm{OH}}}\limits_{{\rm{ethanol}}} {\rm{ + }}\mathop {{\rm{2 [O]}}}\limits_{{\rm{nascent~ oxygen}}} \mathrel{\mathop{\kern0pt\longrightarrow} \limits_{{\rm{Heat}}}^{{\rm{Acidified }}{{\rm{K}}_{\rm{2}}}{\rm{C}}{{\rm{r}}_{\rm{2}}}{{\rm{O}}_{\rm{7}}}}} \mathop {{\rm{C}}{{\rm{H}}_{\rm{3}}}{\rm{COOH}}}\limits_{{\rm{ethanoic~ acid}}} {\rm{ + }}\mathop {{{\rm{H}}_{\rm{2}}}{\rm{O}}}\limits_{{\rm{water}}} $$
3.Reaction with sodium metal:
Ethanol reacts with sodium to form SODIUM ETHOXIDE and liberate HYDROGEN gas.
$$2\mathop {{{\rm{C}}_{\rm{2}}}{{\rm{H}}_{\rm{5}}}{\rm{OH}}}\limits_{{\rm{ethanol}}} {\rm{ + }}\mathop {{\rm{2 Na}}}\limits_{{\rm{sodium}}} \buildrel {} \over
\longrightarrow 2\,\,\mathop {{{\rm{C}}_{\rm{2}}}{{\rm{H}}_{\rm{5}}}{\rm{ONa}}}\limits_{{\rm{sodium~ ethoxide}}} {\rm{ + }}\mathop {{{\rm{H}}_{\rm{2}}}}\limits_{{\rm{hydrogen~ gas}}} $$
4.Dehydration of Ethanol
Ethanol loses water molecule when heated at 443 K in the excess of concentrated sulphuric acid and forms ethene.
$$\mathop {{{\rm{C}}_{\rm{2}}}{{\rm{H}}_{\rm{5}}}{\rm{OH}}}\limits_{{\rm{ethanol}}} \mathrel{\mathop{\kern0pt\longrightarrow}
\limits_{{\rm{443 K}}}^{{\rm{conc}}{\rm{. }}{{\rm{H}}_{\rm{2}}}{\rm{S}}{{\rm{O}}_{\rm{4}}}}} \mathop {{\rm{C}}{{\rm{H}}_{\rm{2}}}{\rm{ = C}}{{\rm{H}}_{\rm{2}}}}\limits_{{\rm{ethene}}} {\rm{ + }}\mathop {{\rm{ }}{{\rm{H}}_{\rm{2}}}{\rm{O}}}\limits_{{\rm{water}}} $$
HARMFUL EFFECTS OF DRINKING ALCOHOL:
1.Methanol causes poisoning and loss of eyesight.
2.A person becomes addicted to alcohol if it is consumed regularly.
3.A person loses sense of discrimination.
4.Excessive intake of alcohol damages liver and may cause death.
CARBOXYLIC ACIDS:
The compounds of carbon, hydrogen and oxygen which contain carboxyl (–COOH) as principal functional group are called carboxylic acids.
General Formula - CnH2n+1COOH
HOMOLOGOUS SERIES OF CARBOXYLIC ACIDS:
MOLECULAR FORMULA |
IUPAC NAME |
COMMON NAME |
HCOOH | Methanoic Acid | Formic Acid |
CH3COOH | Ethanoic Acid | Acetic Acid |
C2H5COOH | Propanoic Acid | Propionic Acid |
C3H7COOH | Butanoic Acid | Butyric Acid |
VINEGAR:
Dilute solution of acetic acid in water that contains 5% to 8% of acetic acid is termed as vinegar.
PHYSICAL PROPERTIES OF ACETIC ACIDS:
1.Physical State: Colourless liquid
2.Boiling point: 391 K (118 OC)
3.Solubility: Readily soluble in water
CHEMICAL PROPERTIES OF ETHANOIC ACID:
1.Reaction with Metal Hydroxides:
Forms metal ethanoate and H2O
$${\rm{C}}{{\rm{H}}_{\rm{3}}}{\rm{COOH}}\,{\rm{ + }}\,{\rm{NaOH}}\buildrel {} \over
\longrightarrow \mathop {{\rm{C}}{{\rm{H}}_{\rm{3}}}{\rm{COONa}}}\limits_{{\rm{SODIUM ~ ETHANOATE}}} {\rm{ + }}\,{{\rm{H}}_{\rm{2}}}{\rm{O}}$$
2.Reaction with Metal Carbonates or Metal Hydrogen carbonates:
Forms metal ethanoate and H2O, and liberate CO2 gas
$${\rm{2}}\,{\rm{C}}{{\rm{H}}_{\rm{3}}}{\rm{COOH + }}\,{\rm{N}}{{\rm{a}}_{\rm{2}}}{\rm{C}}{{\rm{O}}_{\rm{3}}}\buildrel {} \over \longrightarrow \mathop {{\rm{2 C}}{{\rm{H}}_{\rm{3}}}{\rm{COONa}}}\limits_{{\rm{SODIUM ~ ETHANOATE}}} \,{\rm{ + }}{{\rm{H}}_{\rm{2}}}{\rm{O + C}}{{\rm{O}}_{\rm{2}}}$$
$${\rm{C}}{{\rm{H}}_{\rm{3}}}{\rm{COOH}}\,{\rm{ + }}\,{\rm{NaHC}}{{\rm{O}}_{\rm{3}}}\buildrel {} \over
\longrightarrow \mathop {{\rm{C}}{{\rm{H}}_{\rm{3}}}{\rm{COONa}}}\limits_{{\rm{SODIUM~ETHANOATE}}} {\rm{ + }}\,{{\rm{H}}_{\rm{2}}}{\rm{O + C}}{{\rm{O}}_{\rm{2}}}$$
3.Reaction with Alcohols (Esterification):
Ethanoic Acid reacts with alcohols on heating in the presence of concentrated H2SO4 to produce ester and water.
$$\mathop {{\rm{C}}{{\rm{H}}_{\rm{3}}}{\rm{COOH}}}\limits_{{\rm{ethanoic~ acid}}} {\rm{ + }}\mathop {{{\rm{C}}_{\rm{3}}}{{\rm{H}}_{\rm{7}}}{\rm{OH}}}\limits_{{\rm{propanol}}} \mathrel{\mathop{\kern0pt\longrightarrow}
\limits_{{\rm{Heat}}}^{{\rm{conc}}{\rm{. }}{{\rm{H}}_{\rm{2}}}{\rm{S}}{{\rm{O}}_{\rm{4}}}}} \mathop {{\rm{C}}{{\rm{H}}_{\rm{3}}}{\rm{COO}}{{\rm{C}}_{\rm{3}}}{{\rm{H}}_{\rm{7}}}}\limits_{{\rm{propyl ~ethanoate}}} {\rm{ + }}{{\rm{H}}_{\rm{2}}}{\rm{O}}$$