Carbon And its Compounds-F

CloseAn oxidising agent (or oxidant) is a substance that adds oxygen to another substance or removes hydrogen from it. In the process, the oxidising agent itself gets reduced. Examples: KMnO₄, K₂Cr₂O₇.

CloseEthanol (C₂H₅OH) contains the hydroxyl group (–OH), which is the functional group of alcohols. –CO– is a ketone, –CHO is an aldehyde, and –COOH is a carboxylic acid.

CloseEthanol (C₂H₅OH) is the second member of the alcohol homologous series (general formula CₙH₂ₙ₊₁OH). All alcohols contain the –OH functional group attached to a carbon chain.

CloseSubstitution reactions are characteristic of saturated hydrocarbons (alkanes). In these reactions, one or more hydrogen atoms are replaced by other atoms (e.g., chlorine). Unsaturated hydrocarbons typically undergo addition reactions, not substitution.

CloseEthanol (C₂H₅OH) has a melting point of -114°C and boiling point of 78°C. At room temperature (around 25°C), it is a clear, colourless liquid. Methanol is also a liquid; only methane, ethane are gases.

CloseAlcohols react with sodium metal to liberate hydrogen gas. The reaction is: 2R–OH + 2Na → 2R–ONa + H₂↑. This is similar to the reaction of water with sodium but slower. Hydrogen gas is released as bubbles.

CloseMethane (CH₄) reacts with chlorine in the presence of sunlight to undergo substitution. The first step produces chloromethane (CH₃Cl) and hydrogen chloride (HCl): CH₄ + Cl₂ → CH₃Cl + HCl. Further substitution can produce dichloromethane, chloroform, and carbon tetrachloride.

CloseLong-term excessive alcohol consumption causes serious health issues including liver damage (cirrhosis), brain damage, heart disease, pancreatitis, addiction, and increased risk of cancers. It does not promote growth, energy, or immunity.

CloseAlkaline KMnO₄ (potassium permanganate) is a strong oxidising agent. It oxidises ethanol first to ethanal (aldehyde) and then to ethanoic acid (carboxylic acid). The purple colour of KMnO₄ disappears as it gets reduced.

CloseHydrogenation adds hydrogen across the double bonds of unsaturated vegetable oils in the presence of a nickel catalyst. This converts liquid oils into semi-solid saturated fats (like vanaspati ghee or margarine).

ClosePure ethanol is toxic if consumed and can cause health problems. Additionally, ethanol is more expensive than petrol, has lower energy density, and its large-scale production competes with food crops. However, it is used as a fuel additive (gasohol).

CloseAcidified K₂Cr₂O₇ (orange) is an oxidising agent. It oxidises primary alcohols first to aldehydes and then further to carboxylic acids. The colour changes from orange to green (Cr³⁺). For ethanol, it produces ethanal and then ethanoic acid.

CloseVanaspati ghee (vegetable ghee) is produced by hydrogenation of unsaturated vegetable oils. Hydrogen gas is passed through the oil at high temperature and pressure using a nickel catalyst, converting double bonds to single bonds.

CloseDehydration of ethanol to ethene requires heating with concentrated H₂SO₄ at approximately 443 K (170°C). At lower temperatures (413 K or 140°C), ethoxyethane (diethyl ether) is formed instead. 373 K is boiling point of water.

CloseUnsaturated hydrocarbons (with double or triple bonds) characteristically undergo addition reactions. Atoms or groups add across the multiple bond, converting it to a single bond. Examples: hydrogenation, halogenation, addition of water. Substitution is typical for saturated hydrocarbons.

CloseComplete oxidation of ethanol (CH₃CH₂OH) using strong oxidising agents like KMnO₄ or K₂Cr₂O₇ produces ethanoic acid (CH₃COOH). The carbon chain length remains the same (two carbons). Methanoic acid has one carbon, propanoic has three.

CloseUnsaturated fatty acids (found in vegetable oils, nuts, fish) are considered healthier than saturated fats. They help reduce bad cholesterol (LDL) and lower the risk of heart disease, provided they are not hydrogenated into trans fats.

CloseEthene (C₂H₄) is the simplest alkene, containing a carbon-carbon double bond (–C=C–). Alkynes have triple bonds, alkanes have single bonds, and alcohols contain –OH.

CloseEthanol is an excellent solvent for many organic compounds that do not dissolve in water. In medicines (tinctures, cough syrups, antiseptics), it dissolves active ingredients and also acts as a preservative. It is not primarily used as a fuel or catalyst in medicines.

CloseEthanol (CH₃CH₂OH) is converted to ethanoic acid (CH₃COOH) by gaining oxygen (or losing hydrogen). This is an oxidation reaction. The carbon atom bonded to –OH changes from oxidation state –1 to +3.

CloseIn a substitution reaction with alkanes, a chlorine atom replaces one hydrogen atom from the hydrocarbon. For example: CH₄ + Cl₂ → CH₃Cl + HCl. Chlorine does not replace carbon, nitrogen, or oxygen in typical substitution reactions.

CloseSodium metal reacts with ethanol to form sodium ethoxide (C₂H₅ONa) and hydrogen gas: 2C₂H₅OH + 2Na → 2C₂H₅ONa + H₂↑. Sodium hydroxide does not react with ethanol to form sodium ethoxide (it would require removing water).

CloseVegetable oils are composed of triglycerides containing unsaturated fatty acids (with one or more carbon-carbon double bonds). These double bonds keep the oil liquid at room temperature. Saturated chains would make them solid (like animal fats).

CloseMethane reacts with chlorine in the presence of ultraviolet (UV) light (sunlight). UV light provides the energy to break the Cl–Cl bond, generating chlorine free radicals that initiate the substitution reaction. This is a free radical substitution reaction.

CloseIn chlorination of methane, a chlorine atom replaces a hydrogen atom from methane. No addition across a multiple bond occurs because methane has no double bond. This is a typical substitution reaction of alkanes.

CloseHydrogenation adds hydrogen across the double or triple bonds of unsaturated hydrocarbons. Alkenes become alkanes (saturated), and alkynes become alkenes and then alkanes. For example: C₂H₄ + H₂ → C₂H₆ (ethene to ethane).

CloseDehydration of ethanol (removal of water) with concentrated H₂SO₄ at 443 K produces ethene (C₂H₄). The reaction is: C₂H₅OH → C₂H₄ + H₂O. Removal of water from an alcohol yields an alkene.

CloseA substitution reaction is defined as a chemical reaction in which an atom or group of atoms in a molecule is replaced by another atom or group. For example: CH₄ + Cl₂ → CH₃Cl + HCl (Cl replaces H).

CloseEthanol is a specific type of alcohol (ethyl alcohol). It is not an aldehyde, acid, or ketone. The term “alcohol” refers to the entire class; ethanol is one member. Ethanal is an aldehyde, ethanoic acid is an acid, and propanone is a ketone.

CloseEthyne (acetylene) mixed with air is explosive. For welding, a controlled mixture of ethyne and pure oxygen is used (oxy-acetylene flame). An air mixture would be dangerous and unpredictable due to the presence of nitrogen.

CloseAnimal fats (butter, lard, tallow) are rich in saturated fatty acids (no double bonds), which make them solid at room temperature. Vegetable oils contain more unsaturated fatty acids and are liquid. Both are esters (triglycerides), but the key difference is saturation.

CloseAlcohols react with reactive metals like sodium, potassium, magnesium, and aluminium to liberate hydrogen gas. The reaction is: 2R–OH + 2Na → 2R–ONa + H₂↑. They do not neutralise bases (acids do).

CloseHydrogenation is the addition of hydrogen (H₂) across a double or triple bond. Since atoms add across the multiple bond without removing any atom, it is classified as an addition reaction, not substitution, oxidation, or combustion.

CloseConsuming small to moderate amounts of dilute ethanol (e.g., beer, wine) causes intoxication (drunkenness) due to its effects on the central nervous system—slurred speech, impaired coordination, and lowered inhibitions. Large amounts can cause coma or death.

CloseConcentrated H₂SO₄ is a strong dehydrating agent. When ethanol is heated with it, water is removed (dehydration) to form ethene. The reaction is: C₂H₅OH → C₂H₄ + H₂O. Concentrated H₂SO₄ also acts as a catalyst.

CloseA catalyst increases or decreases the rate of a chemical reaction without itself being consumed or chemically changed at the end of the reaction. It may be involved in intermediate steps but is regenerated. Catalysts do not produce heat (reactions do).

CloseThe reaction of ethanol with sodium metal gives sodium ethoxide (C₂H₅ONa) and hydrogen gas: 2C₂H₅OH + 2Na → 2C₂H₅ONa + H₂↑. Sodium chloride would require chlorine, sodium hydroxide requires water, sodium carbonate requires CO₂.

CloseFinely divided nickel is the most common catalyst used in the hydrogenation of vegetable oils. Other catalysts like platinum or palladium are also effective but more expensive. Iron is used in Haber process, zinc and copper are not typical for this reaction.

CloseEthene (C₂H₄) has a carbon-carbon double bond (C=C) consisting of one sigma bond and one pi bond. It also has four C–H single bonds, but the characteristic bond is the double bond between the two carbons.

CloseIn the reaction with ethanol, concentrated H₂SO₄ acts as a dehydrating agent, removing water (H₂O) from the alcohol molecule to form ethene. It also acts as a catalyst, but its primary role here is dehydration. It can also be an oxidising agent but not in this reaction.

CloseThe conversion of an alcohol to an alkene involves the removal of water (H₂O) from the alcohol molecule. This is specifically called dehydration. Example: C₂H₅OH → C₂H₄ + H₂O. Oxidation would give aldehyde/acid, not alkene.

CloseIn free radical substitution (e.g., chlorination of methane), multiple products form because hydrogen atoms are replaced sequentially. First, CH₃Cl (chloromethane) forms, but further substitution gives CH₂Cl₂, CHCl₃, and CCl₄. Each step replaces one more hydrogen.

CloseAn oxy-acetylene flame (oxygen + ethyne) reaches temperatures around 3,500°C (6,330°F), which is hot enough to melt and weld metals like steel. The high temperature comes from the complete combustion of ethyne.

CloseWhen ethanol reacts with sodium, the sodium atom replaces the hydrogen atom of the –OH group. This is a substitution reaction: C₂H₅OH + Na → C₂H₅ONa + ½H₂. The H is replaced by Na. It is also a metal displacement but is classified as substitution in organic chemistry.

CloseEthanol has wide commercial uses: alcoholic beverages, antiseptics, solvents in medicines and perfumes, fuel additive, industrial solvent, and in the manufacture of many chemicals. Fertilizers and explosives do not primarily use ethanol.

CloseSaturated hydrocarbons (alkanes) are relatively unreactive under normal conditions. They do not undergo addition reactions (no multiple bonds). They burn readily (combustion) and undergo substitution with halogens in sunlight, but are generally considered chemically inert compared to alkenes/alkynes.

CloseAbsolute alcohol is pure ethanol (99.9% or anhydrous) containing less than 1% water. Rectified spirit is about 95% ethanol (azeotrope). Industrial alcohol is denatured (poisoned). Dilute alcohol contains significant water.

CloseEthanol is completely miscible with water (soluble in all proportions). This is due to hydrogen bonding between the –OH group of ethanol and water molecules. Unlike oils, ethanol does not form a separate layer when mixed with water.

CloseAbsolute (pure) ethanol is highly toxic. Even a small amount (a few ounces) can cause severe poisoning, respiratory depression, coma, and even death, especially in children. It is not safe, beneficial, or neutral. Dilute ethanol (beer/wine) in very small amounts may be consumed safely by adults, but absolute alcohol is dangerous.