PERIOD 2 AND 3 : PHYSICAL AND CHEMICAL PROPERTIES OF ALKANOIC ACID
1. Alkanoic acds are very soluble in water each alkanoic acid forms hydrogen bond with water molecule. The solubility of alkanoic acid in water decreases as the carbon atom increases. Threrefore, lower members are more soluble in water.
They have high boiling and melting points.their two pairs of hydrogen bond per molecule of alkanoic acid. The boiling and melting points increase as the carbon chain increases.
they turn blue litmus paper red.
1. Reaction with active metals
Alkanoic acids react with active metals to liberate hydrogen gas.
2RCOOH + Zn (RCOO)2Zn + H2
2CH3COOH + Zn (CH3COO)2Zn + H2
Reaction with base.
Alkanoic acids react with bases to form salt and water.
RCOOH + NaOH RCOONa + H2O
e.g CH3CH2COOH + NaOH CH3CH2COONa + H2O
Alkanoic acid liberate carbon(iv) oxide from metallic trioxocarbonate (iv) or hydrogentrioxocarbonate (iv)
2RCOOH + CaCO3 (RCOO)2Ca + H2O + CO2
Alkanoic acid reacts reversibly with alkanol in the presence of tetraoxosulphate (vi) acid to form alkanoate (ester). On heating the mixture, a fruity of fragrance aroma is observed. Tetraoxosulphate (vi) acid serves as catalyst. this reaction is called esterification.
RCOOH + R1OH RCOOR1 + H2O
In this reaction the alkyl group of alkanol replaces the acidic hydrogen of the alkanoic acid
Ethanoic acid reacts with ethanol to give ethyl ethanoate.
CH3COOH + CH3CH2OH CH3COOCH2CH3 + H2O
Alkanoic acid are reduced to alkanol by lithium tetrahydridoaluminate (iii) (LiAlH4)
State three physical properties of alkanoic acid.
Explain why methanoic acid is very soluble in water
With the aid of a chemical equation only, show how zinc reacts with methanoic acid
1. SOURCES, NOMENCLATURE.
2. PREPARATION AND STRUCTURE.
3. PHYSICAL AND CHEMICAL PROPERTIES AND USES.
PERIOD 1: SOURCES, NOMENCLATURE
Alkanoates are found widely in nature. Short carbon chain simple alkanoates exist as liquids and have a characteristic pleasant smel. They occur in essential oils, many fruits and floers and sometimes called fruit essence because of the pleasant odours. The general molecular formula is CnH2n+1COOCnH2n+1. The structural formula is