Introduction To Organic Chemistry Grade 10 Sample Questions PDF

CHEMISTRY GRADE 10 SAMPLE QUESTIONS AND SHORT NOTES FOR GRADE 12 Introduction to Organic Chemistry THESE QUESTIONS ARE PROVIDED TO SEE IF YOU HAVE MASTERED THE CONCEPTS OF THE CHAPTER “INTRODUCTION TO ORGANIC CHEMISTRY” COVERED IN GRADE 10. DO NOT USE YOUR BOOK OR...

CHEMISTRY GRADE 10 SAMPLE QUESTIONS AND SHORT NOTES FOR GRADE 12 Introduction to Organic Chemistry THESE QUESTIONS ARE PROVIDED TO SEE IF YOU HAVE MASTERED THE CONCEPTS OF THE CHAPTER “INTRODUCTION TO ORGANIC CHEMISTRY” COVERED IN GRADE 10. DO NOT USE YOUR BOOK OR NOTES ON YOUR FIRST ATTEMPT AT THESE PROBLEMS. 1. Classify the following molecule: A. Primary B. Secondary C. Tertiary D. Quaternary Explanation: Carbon atoms can be classified as primary (1°), secondary (2°), tertiary (3°) and quaternary (4°) if they are bonded to one, two, three and four carbon atoms, respectively. Example: Primary alcohols are those alcohols which have the hydroxyl group connected to a primary carbon. They can also be defined as a molecule containing a “–CH2OH” group. Secondary alcohols are those in which the carbon atom bonded to the hydroxyl group is attached to two alkyl groups or contains an –OH group bonded to a secondary carbon atom. Tertiary alcohols are those in which the carbon atom bonded to the hydroxyl group is attached to three hydrocarbon (alkyl) groups or contain –OH group attached to a tertiary carbon atom. 1 2. Select the IUPAC name for: (CH3)2CHCH(OH)CH2C(CH3)3. A. 2,5,5-trimethyl-3-hexanol C. 1,1,4,4-pentamethylbutanol B. 1,1-dimethylisopentanol D. 2,5-dimethyl-4-hexanol 3. Which is NOT a physical property of alcohols or phenols? A. Phenols are generally only slightly soluble in water. B. The solubilities of normal primary alcohols in water decrease with increasing molecular weight. C. The hydroxyl group of an alcohol is nonpolar. D. Due to hydrogen bonding, boiling points of alcohols are much higher than those of corresponding alkanes. E. Boiling points of normal primary alcohols increase with increasing molecular weight. Physical Properties of Alcohols The hydroxyl group in an alcohol is polar due to the high electronegativity of oxygen. As a result, there is significant hydrogen bonding in alcohols. Due to the hydrogen bonding in alcohols, they have higher melting and boiling points than hydrocarbons of comparable molecular size (mass). Hydrogen bonding is also the cause for even lower members to be liquids at room temperature. The boiling point of more branched isomer is lower than that of its isomeric straight- chain alcohol. 4. Which alkene should be hydrolyzed in the presence of an acid catalyst to form 2-butanol? Ans. 2-butene Preparation of Alcohols The general laboratory methods of preparation of alcohols are: I. Acid-catalyzed hydration of alkenes: Example: II. Hydrolysis of alkyl halides: Warming alkyl halides with sodium hydroxide forms alcohols 2  III. Hydrolysis of Esters: Heating esters with potassium hydroxide produce alcohols. 5. Which alcohol can be prepared by hydrolyzing n-propylbutanoate with KOH? Ans. 1-propanol 6. What type of bond cleavage oxidation of primary alcohols using Na2CrO4? 7. What type of bond cleavage oxidation of primary alcohols using Na2CrO4? Explanation: The reactions of alcohols involving the –O–H bond cleavage are: A. Alcohols react with strongly electropositive metals like Na, K and Ca to form alkoxides and liberating H2 gas. B. Oxidation of alcohols The oxidation products of alcohols depend on the type of alcohol and the nature of oxidizing agents. Oxidation of alcohols is a very important method for the production of other oxygen-containing compounds of hydrocarbons, such as aldehydes, ketones and carboxylic acids. I. Oxidation of primary alcohols in the presence of mild oxidizing agents yields aldehydes 3  Strong oxidizing agents, such as acidified KMnO4 or K2Cr2O7and CrO3 in H2SO4, oxidize primary alcohol first to aldehydes and then to carboxylic acids. It is difficult to stop the reaction at the aldehyde stage. II. Oxidation of secondary alcohols yields ketones III. Tertiary alcohols and ketones are generally resistant to oxidation. However, they can undergo oxidation under drastic conditions to form a mixture of carboxylic acids. C. Esterification: Carboxylic acids react with alcohols to form esters. This reaction is known as esterification. 4  The reactions of alcohols involving the – C – O bond cleavage include I. Dehydration of alcohols: Heating alcohols in the presence of dehydrating agents, like concentrated H2SO4, yield alkenes. II. Reactions of alcohols with hydrogen halides produce alkyl halides: 8. Which of the following compounds is a ketone? The general structural formula of ketones is RCOR’ where R and R’ may be same or different. 9. The compounds CH3OH and CH3COOH react in the presence of an acid catalyst to form: A. A carboxylic acid C. An aldehyde B. A ketone D. An ester Carboxylic acids react with alcohols to form esters. This reaction is known as esterification. 10. Which hydrocarbon is the main constituent of natural gas and biogas? A. C4H10 B. CH4 C. C2H6 D. C6H14 Natural gas mainly contains methane (more than 90%), ethane, propane, butane and small quantities of higher alkanes 11. Alcohols that yield ketones on oxidation are classified as: A. Primary alcohols B. Secondary alcohols C. Dihydric alcohols D. Trihydric alcohols 5