Carbon compounds of daily use, and coal, petroleum and natural gas
Methanol, ethanol, formalin, acetone and acetic acid are carbon compounds we use daily. Most organic compounds come from coal, petroleum and natural gas, or from plants and fermentation.
Alcohols you should know
| Name | Formula | Notes |
|---|---|---|
| Methanol (wood alcohol) | CH₃OH | Once made by heating wood without air; now from CO and H₂. Used to make acetic acid, adhesives, fibres and plastics, and as a fuel. Poisonous |
| Ethanol | C₂H₅OH | Used in medicines and as a solvent; rectified spirit is 95% ethanol |
| 2-propanol (rubbing alcohol) | CH₃CH(OH)CH₃ | Used as rubbing alcohol on the skin |
| Glycerin (1,2,3-propanetriol) | CH₂(OH)CH(OH)CH₂OH | Has three -OH groups; used in skin creams and soaps |
Making methanol, ethanol and acetic acid
Alcohols dissolve in water because their -OH groups form hydrogen bonds with water molecules.
- 1CO(g) + 2H₂(g) → CH₃OH(g)Methanol: at about 400 °C and 200 to 300 atm, over a ZnO and Cr₂O₃ catalyst
- 2★C₆H₁₂O₆(aq) → 2C₂H₅OH(aq) + 2CO₂(g)Ethanol: fermentation of glucose (from grapes, barley or sugarcane molasses) by enzymes in yeast
- 3CH₃CH₂OH + 2[O] → CH₃COOH + H₂OAcetic acid: oxidising ethanol with potassium dichromate (K₂Cr₂O₇) and concentrated H₂SO₄. [O] means oxygen from the oxidising agent
★ key step
Aldehydes, ketones and carboxylic acids of daily use
| Compound | Formula | Where you meet it |
|---|---|---|
| Methanal (formaldehyde) | HCHO | Formalin, its solution in water, preserves biological specimens |
| Vanillin | Contains an aldehyde group | Vanilla flavour in ice cream and sweets |
| Propanone (acetone) | CH₃COCH₃ | A solvent; nail polish remover |
| Ethanoic acid (acetic acid) | CH₃COOH | Vinegar; a preservative for pickles |
| Methanoic acid (formic acid) | HCOOH | Ant stings (Latin formica means ant) |
| Butyric acid | CH₃CH₂CH₂COOH | The smell of rancid (stale) butter |
| Lactic acid | CH₃CH(OH)COOH | Sour milk; made in muscles during hard exercise |
| Citric acid | A carboxylic acid | Lemons, oranges and other citrus fruits |
| Ascorbic acid (vitamin C) | A weak organic acid. Your NIOS lesson lists it with carboxylic acids, but it has no -COOH group | Amla, lemons and oranges |
Sources of carbon compounds
| Source | What we get from it |
|---|---|
| Plants and animals | Carbohydrates, starch, oils, proteins, medicines |
| Coal | Coke, coal gas, and compounds such as benzene, phenol and naphthalene |
| Petroleum | Petrol, diesel, kerosene, lubricating oils, wax, LPG |
| Natural gas | Mainly methane: CNG for vehicles, piped gas for cooking, raw material for fertilisers |
Activity: mark coal and petroleum regions of India on a map
- 1Take an outline map of India. Use one colour for coal and another for oil and gas.
- 2Coal: mark Jharia and Bokaro (Jharkhand), Raniganj (West Bengal), Talcher (Odisha), Korba (Chhattisgarh), Singrauli (Madhya Pradesh) and Singareni (Telangana).
- 3Petroleum and natural gas: mark Digboi in Assam (India's oldest oil field), Ankleshwar and Kalol in Gujarat, and Barmer in Rajasthan. Also mark Mumbai High, in the sea off Mumbai, and the Krishna-Godavari basin in Andhra Pradesh.
- 4★Look at your finished map.Most coal lies in eastern and central India; most oil and gas lies in the west, the north-east and offshore
★ key step
Why we must save fossil fuels
- Coal, petroleum and natural gas formed from the remains of plants and animals over millions of years. Once used, they cannot be replaced quickly.
- We use them far faster than they form, so they are running short.
- Burning them adds carbon dioxide to the air, and poor burning also gives carbon monoxide.
- Save them: use public transport, switch off engines at red lights, cook with lids on pans, and use solar energy where you can.
CNG buses and autos, and piped cooking gas in many cities, run on methane from natural gas. The vinegar in your kitchen keeps pickles from spoiling, and formalin keeps specimens in a school laboratory.
3 marks: “Sugarcane molasses can be turned into a fuel that is mixed with petrol. Name the fuel, the process and the living thing that brings it about, and write the equation starting from glucose.” Ethanol, made by fermentation, using yeast (its enzymes). C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂.
2 marks: “Why is methanol called wood alcohol? How is it made today?” It was first obtained by heating wood without air. Today: CO + 2H₂ → CH₃OH at about 400 °C and 200 to 300 atm over a ZnO and Cr₂O₃ catalyst.
2 marks: “Coal and petroleum are both called sources of organic compounds. Name two substances obtained from each.” Coal: coke, benzene, naphthalene or phenol (any two). Petroleum: petrol, diesel, kerosene, wax or LPG (any two).
Yeast + glucose = ethanol + CO₂. Methanol is wood alcohol: never drink it.