In the previous section, we completed a discussion on combustion and thermal cracking. In this section we will see some important organic compounds.
• They contain the OH functional group.
• CH3 ㅡOH (Methanol) and CH3 ㅡCH2 ㅡOH (Ethanol) are two important alcohols.
• Methanol is commonly known as wood spirit
• Ethanol is commonly known as grape spirit
■ First we will see methanol in detail:
Uses of methanol
1. Methanol is used as a solvent in the manufacture of paint
2. It is also used as a reactant in the manufacture of varnish and formalin
• So it is a very valuable industrial substance. It is very poisonous too.
Industrial preparation of methanol
• Methanol is industrially prepared by the reaction between carbon monoxide with hydrogen in the presence of catalysts. The equation is shown below:
Note that 3 items are required for the reaction:
(i) Catalyst
(ii) Temperature of 573 k. (Details about the units of temperature can be seen here)
(iii) Pressure of 200 atm (Details about pressure can be seen here)
■ Next we will see ethanol:
Uses of ethanol
1. Ethanol is used as an organic solvent
2. It is used in the manufacture of various organic compounds and paints.
3. It can also be used as a fuel by itself or in combination with other compounds.
• That is., a liquid containing crystals of sugar
2. When the solid sugar crystals are removed, a liquid is left behind.
• This liquid is a concentrated solution of sugar.
• This concentrated solution of sugar is called molasses.
3. This molasses is diluted and then fermented.
• Fermentation is done by adding yeast. The process of fermentation lasts for a few days.
• During the fermentation, some reactions occur due to the presence of enzymes in the yeast.
• The enzymes are: Invertase and Zymase.
The reactions are shown below:
4. The reaction takes place in stages:
• First the sugar is converted into glucose and fructose.
♦ This is accomplished with the help of the enzyme invertase
♦ Note that glucose and fructose have the same molecular formula.
♦ But they have different structural formulae
• Then the gucose and fructose are converted into ethanol.
♦ This is accomplished with the help of the enzyme zymase
5. The ethanol thus obtained will be about 8-10% strong.
• That is., if there are a total of 100 molecules in a sample, only 8 to 10 of them will be ethanol molecules.
• This ethanol is called wash.
6. Wash is subjected to fractional distillation. Some basics about fractional distillation can be seen here.
• By this process, we get 95.6% strong ethanol solution. It is known as rectified spirit.
7. Rectified spirit is a very important industrial substance. So it would be produced on a large scale.
• This rectified spirit meant for industrial purpose should not be used as a beverage.
• To prevent it's use as a beverage, poisonous substances are added to those ethanol which are meant for industrial purposes.
• This ethanol is called denatured spirit.
8. 99.5% ethanol is known as absolute alcohol.
• A mixture of absolute alcohol and petrol is known as power alcohol. It is used as fuel in automobiles.
9. What we saw above is the production of ethanol from molasses.
• Ethanol can be manufactured from starchy substances like barley, rice, tapioca etc., also.
1. IUPAC name: Methanoic acid
• Common name: Formic acid
• Formula: H ㅡCOOH
• Structural formula: See fig.15.20(a) below
2. IUPAC name: Ethanoic acid
• Common name: Acetic acid
• Formula: CH3 ㅡCOOH
• Structural formula: See fig.15.20(b) below
3. IUPAC name: Propanoic acid
• Common name: Propionic acid
• Formula: CH3 ㅡCH2 ㅡCOOH
• Structural formula: See fig.15.20(c) below
• Many substances obtained from nature contains carboxylic acids. For example:
• The product obtained as a result of the fermentation of fruits will contain Ethanoic acid (Acetic acid)
• About 5-8% strong ethanoic acid is called vinegar.
• Carboxylic acids are usually prepared by the oxidation of alcohols.
♦ Vinegar can be prepared from ethanol in this way
• Carboxylic acids containing 12 or more carbon atoms are called fatty acids.
• Note that when the number of carbon atoms become 2, the 'meth' becomes 'eth'
• Vinegar can be obtained by the fermentation of ethanol in the presence of air using the bacteria acetobactor
Uses of ethanoic acid:
• In the manufacture of rayon
• In the rubber and silk industry
• Gives flavour to food items
• As a preservative
• We have seen the details about both alcohols and carboxylic acids above.
■ So let us see an example of a reaction between them:
• Consider a carboxylic acid: Ethanoic acid
• Consider a alcohol: Ethanol
• The equation of the reaction between them is shown below:
• Note how the two oxygen atoms come together
• From the structural formula of the product Ethyl ethanoate, it is clear that, the functional group in esters is: ㅡCOOㅡ
• We have seen that fatty acids are carboxylic acids having 12 or more carbon atoms
♦ Palmitic acid and stearic acid are fatty acids
♦ Because they are carboxylic acids having 12 or more carbon atoms
• Consider an alcohol: Glycerol
♦ It reacts with palmitic acid and stearic acid.
♦ The products are oils and fats.
♦ Oils and fats are esters
Solved example 15.6:
Examine the structural formulae given below and identify the esters. Write the chemicals required for the manufacture of each of those esters.
1. CH3 ㅡCH2ㅡCOOㅡCH3
2. CH3 ㅡCH2ㅡCOOH
3. CH3 ㅡCH2ㅡCOㅡCH3
4. CH3 ㅡOH
5. CH3 ㅡCH2ㅡCH2ㅡOH.
6. CH3 ㅡCOOH
7. CH3 ㅡCH2ㅡCH2ㅡCOOㅡCH3
Solution:
Esters contain the 'ㅡCOOㅡ' functional group. So (1) and (7) are esters
1. CH3 ㅡCH2ㅡCOOㅡCH3
• In the 'ㅡCOOㅡ', the CO comes from a carboxylic acid
• The second O comes from an alcohol
• So we can split it as: CH3 ㅡCH2ㅡCO│OㅡCH3 .
• On the left side, we have 3 carbon atoms. So it indicates Propanoic acid
• On the right side, we have 1 carbon atom. So it indicates Methanol
• So the chemicals required are: Propanoic acid and methanol
7. CH3 ㅡCH2ㅡCH2ㅡCOOㅡCH3
• In the 'ㅡCOOㅡ', the CO comes from a carboxylic acid
• The second O comes from an alcohol
• So we can split it as: CH3 ㅡCH2ㅡCH2ㅡCO│OㅡCH3 .
• On the left side, we have 4 carbon atoms. So it indicates Butanoic acid
• On the right side, we have 1 carbon atom. So it indicates Methanol
• So the chemicals required are: Butanoic acid and methanol
• It is the simplest aromatic compoundstructure. It's name is benzene.
• It has 6 carbon atoms. These carbon atoms are arranged at the corners of a regular hexagon
• But each of those carbon atoms have only one hydrogen atom.
• So to satisfy the valency requirements, there should be 3 double bonds.
• These double bonds will be arranged alternately.
♦ That is., no two double bonds in the structure will come near each other.
■ So there are two possible ways to draw the structure
• In fig.a, the first double bond starts at top left
• In fig.b, the first double bond starts at top right
■ A simple way for drawing the structures is shown in fig.15.22 below
Compounds of Benzene
• All aromatic compounds have a ring structure.
• There are double bonds between alternate carbon atoms
• In benzene, each carbon atom has one hydrogen atom.
• Any one of those hydrogen can be replaced by a functional group.
• Thus we get different aromatic compounds. Some examples are shown in fig.15.23 below:
• These compounds have immense chemical and industrial significance.
• Many useful substances can be prepared from them.
• Coal tar obtained by the distillation of coal in the absence of air is the source of aromatic compounds.
In the next section, we will see some important applications of Chemistry
Alcohols
• We have learned the nomenclature details about alcohols in the previous chapter.• They contain the OH functional group.
• CH3 ㅡOH (Methanol) and CH3 ㅡCH2 ㅡOH (Ethanol) are two important alcohols.
• Methanol is commonly known as wood spirit
• Ethanol is commonly known as grape spirit
■ First we will see methanol in detail:
Uses of methanol
1. Methanol is used as a solvent in the manufacture of paint
2. It is also used as a reactant in the manufacture of varnish and formalin
• So it is a very valuable industrial substance. It is very poisonous too.
Industrial preparation of methanol
• Methanol is industrially prepared by the reaction between carbon monoxide with hydrogen in the presence of catalysts. The equation is shown below:
Note that 3 items are required for the reaction:
(i) Catalyst
(ii) Temperature of 573 k. (Details about the units of temperature can be seen here)
(iii) Pressure of 200 atm (Details about pressure can be seen here)
■ Next we will see ethanol:
Uses of ethanol
1. Ethanol is used as an organic solvent
2. It is used in the manufacture of various organic compounds and paints.
3. It can also be used as a fuel by itself or in combination with other compounds.
Industrial preparation of ethanol
1. During the manufacture of sugar, we get a liquid mixture of sugar crystals.• That is., a liquid containing crystals of sugar
2. When the solid sugar crystals are removed, a liquid is left behind.
• This liquid is a concentrated solution of sugar.
• This concentrated solution of sugar is called molasses.
3. This molasses is diluted and then fermented.
• Fermentation is done by adding yeast. The process of fermentation lasts for a few days.
• During the fermentation, some reactions occur due to the presence of enzymes in the yeast.
• The enzymes are: Invertase and Zymase.
The reactions are shown below:
4. The reaction takes place in stages:
• First the sugar is converted into glucose and fructose.
♦ This is accomplished with the help of the enzyme invertase
♦ Note that glucose and fructose have the same molecular formula.
♦ But they have different structural formulae
• Then the gucose and fructose are converted into ethanol.
♦ This is accomplished with the help of the enzyme zymase
5. The ethanol thus obtained will be about 8-10% strong.
• That is., if there are a total of 100 molecules in a sample, only 8 to 10 of them will be ethanol molecules.
• This ethanol is called wash.
6. Wash is subjected to fractional distillation. Some basics about fractional distillation can be seen here.
• By this process, we get 95.6% strong ethanol solution. It is known as rectified spirit.
7. Rectified spirit is a very important industrial substance. So it would be produced on a large scale.
• This rectified spirit meant for industrial purpose should not be used as a beverage.
• To prevent it's use as a beverage, poisonous substances are added to those ethanol which are meant for industrial purposes.
• This ethanol is called denatured spirit.
8. 99.5% ethanol is known as absolute alcohol.
• A mixture of absolute alcohol and petrol is known as power alcohol. It is used as fuel in automobiles.
9. What we saw above is the production of ethanol from molasses.
• Ethanol can be manufactured from starchy substances like barley, rice, tapioca etc., also.
Carboxylic acids
These are compounds containing carboxylic acid group (ㅡCOOH). We have seen their nomenclature details in the previous chapter. Some examples are:1. IUPAC name: Methanoic acid
• Common name: Formic acid
• Formula: H ㅡCOOH
• Structural formula: See fig.15.20(a) below
2. IUPAC name: Ethanoic acid
• Common name: Acetic acid
• Formula: CH3 ㅡCOOH
• Structural formula: See fig.15.20(b) below
3. IUPAC name: Propanoic acid
• Common name: Propionic acid
• Formula: CH3 ㅡCH2 ㅡCOOH
• Structural formula: See fig.15.20(c) below
 |
| Fig.15.20 |
• The product obtained as a result of the fermentation of fruits will contain Ethanoic acid (Acetic acid)
• About 5-8% strong ethanoic acid is called vinegar.
• Carboxylic acids are usually prepared by the oxidation of alcohols.
♦ Vinegar can be prepared from ethanol in this way
• Carboxylic acids containing 12 or more carbon atoms are called fatty acids.
Industrial preparation of Ethanoic acid
• Ethanoic acid can be manufactured by treating methanol with carbon monoxide in the presence of catalyst. The reaction is shown below:
• Note that when the number of carbon atoms become 2, the 'meth' becomes 'eth'
• Vinegar can be obtained by the fermentation of ethanol in the presence of air using the bacteria acetobactor
Uses of ethanoic acid:
• In the manufacture of rayon
• In the rubber and silk industry
• Gives flavour to food items
• As a preservative
Esters
• Esters are obtained by the reaction between alcohols and carboxylic acids.• We have seen the details about both alcohols and carboxylic acids above.
■ So let us see an example of a reaction between them:
• Consider a carboxylic acid: Ethanoic acid
• Consider a alcohol: Ethanol
• The equation of the reaction between them is shown below:
• From the structural formula of the product Ethyl ethanoate, it is clear that, the functional group in esters is: ㅡCOOㅡ
• We have seen that fatty acids are carboxylic acids having 12 or more carbon atoms
♦ Palmitic acid and stearic acid are fatty acids
♦ Because they are carboxylic acids having 12 or more carbon atoms
• Consider an alcohol: Glycerol
♦ It reacts with palmitic acid and stearic acid.
♦ The products are oils and fats.
♦ Oils and fats are esters
Solved example 15.6:
Examine the structural formulae given below and identify the esters. Write the chemicals required for the manufacture of each of those esters.
1. CH3 ㅡCH2ㅡCOOㅡCH3
2. CH3 ㅡCH2ㅡCOOH
3. CH3 ㅡCH2ㅡCOㅡCH3
4. CH3 ㅡOH
5. CH3 ㅡCH2ㅡCH2ㅡOH.
6. CH3 ㅡCOOH
7. CH3 ㅡCH2ㅡCH2ㅡCOOㅡCH3
Solution:
Esters contain the 'ㅡCOOㅡ' functional group. So (1) and (7) are esters
1. CH3 ㅡCH2ㅡCOOㅡCH3
• In the 'ㅡCOOㅡ', the CO comes from a carboxylic acid
• The second O comes from an alcohol
• So we can split it as: CH3 ㅡCH2ㅡCO│OㅡCH3 .
• On the left side, we have 3 carbon atoms. So it indicates Propanoic acid
• On the right side, we have 1 carbon atom. So it indicates Methanol
• So the chemicals required are: Propanoic acid and methanol
7. CH3 ㅡCH2ㅡCH2ㅡCOOㅡCH3
• In the 'ㅡCOOㅡ', the CO comes from a carboxylic acid
• The second O comes from an alcohol
• So we can split it as: CH3 ㅡCH2ㅡCH2ㅡCO│OㅡCH3 .
• On the left side, we have 4 carbon atoms. So it indicates Butanoic acid
• On the right side, we have 1 carbon atom. So it indicates Methanol
• So the chemicals required are: Butanoic acid and methanol
Aromatic compounds
Consider the aromatic compound shown in fig.15.21(a) below: |
| Fig.15.21 |
• It has 6 carbon atoms. These carbon atoms are arranged at the corners of a regular hexagon
• But each of those carbon atoms have only one hydrogen atom.
• So to satisfy the valency requirements, there should be 3 double bonds.
• These double bonds will be arranged alternately.
♦ That is., no two double bonds in the structure will come near each other.
■ So there are two possible ways to draw the structure
• In fig.a, the first double bond starts at top left
• In fig.b, the first double bond starts at top right
■ A simple way for drawing the structures is shown in fig.15.22 below
 |
| Fig.15.22 |
• All aromatic compounds have a ring structure.
• There are double bonds between alternate carbon atoms
• In benzene, each carbon atom has one hydrogen atom.
• Any one of those hydrogen can be replaced by a functional group.
• Thus we get different aromatic compounds. Some examples are shown in fig.15.23 below:
 |
| Fig.15.23 |
• Many useful substances can be prepared from them.
• Coal tar obtained by the distillation of coal in the absence of air is the source of aromatic compounds.
In the next section, we will see some important applications of Chemistry
No comments:
Post a Comment