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Chapter one: Unsaturated Hydrocarbons Questions and Answers 1. . The first and simplest alkane is a) Ethane b) Propane c) Butane d) Methane 2. Which of the following classes of organic compounds is NOT a hydrocarbon a. Cycloalkanes b) alkenes c) alcohols d) alkanes 3. What organic compound is characterized by the presence of a single bond? a) Alkanes b) alkynes c) alkenes 4. When one hydrogen atom of alkane is removed then it is called? a) Alkane b) alkyl c) alkynes d) saturated hydrocarbons 5. Hydrocarbons combust in abundant oxygen to form: a. Carbon dioxide and carbon monoxide b. Smaller hydrocarbons such as methane c. Carbon dioxide and water d. Carbon and water 6. What is the difference between a. Cyclic an acyclic hydrocarbon? Cyclic: it has rings of carbon atoms or it contains closed chain Acyclic: it has no rings of carbon atoms. Or it contains open chain b. continuous- chain alkane and branched-chain alkane Acyclic alkanes are subdivided as continuous- chain and branched alkanes Continuous- chain alkane: is an alkane in which all carbon atoms are connected in a continuous non-branching chain. Branched-chain alkane: is an alkane in which one or more branches (of carbon atoms) are attached to a continuous chain of carbon atoms 7. What is an alkyl group? Name and draw the structure derived from ethane , propane , and butane An alkyl group is the group of atoms that would be obtained by removing a hydrogen atom from an alkane 1 8. Name each the following compounds using the systematic name (IUPAC) CH3 CH3 | a. CH3CHCH2CH3 | b. CH3CH2CCH2CH3 | C H 3 c. CH3 CH3 CH3 | | | CH3CHCHCH2CHCH3 CH3 CH2CH3 CH3 | | | d. CH3CHCHCH2CHCH2CH2CH3 CH2CH2CH3 | e. CH3CH2CH2CHCH2CH2CH2CH2CH3 f. g. 2 a. b. c. d. e. f. g. 2-methylbutane 3,3-dimethylpentane 2,3,5-trimethylhexane 3-ethyl-2,5-dimethyloctane 4-propylnonane 3,3,6-trimethylnonane 3,3,5-trimethylheptane 9. Complete and balance each of the following combustion reaction of alkanes? A. C5H12 (g) + 8O2 (g) ——> 5 CO2 + 6 H2O B. 2C2H6 (g) + 7O2 (g) ——> 4 CO2 + 6 H2O 10. Pentane has three isomers with the same molecular formula C5H12 A) What is an isomer? Isomers are compounds that have the same molecular formula but that differ in the way the atoms are arranged B) Draw the structural formula of three isomers of pentane 11. Explain the difference between A combustion reaction and halogenation reaction A combustion reaction is a chemical reaction between a substance and oxygen A halogenation reaction is a chemical reaction between a substance and a halogen 12. Draw the structure corresponding to each IUPAC name A) 2, 3-dichlorohexane 3 B) 1 3-dimethylcyclopentane C) Ethylcyclpentane 3-chloro-5-methylhexane 13. Look at the reaction represented by the equation below, classify each reaction as a) Substitution b) Addition c) combustion i. CH2=CH2+H2 ——>CH3CH3 Addition ii. CH3-CH2-CH3 + 5 O2 ——> 3 CO2 + 4 H2O + heat (combustion) iii. CH4 + Cl2 ——> CH3Cl + HCl Substitution 14. What is the general formula of a. Cycloalkane: CnH2n b. Alkanes: CnH2n+2 4 15. Name the following compounds a) b) c) d) Methylcyclopentane Isopropylcyclohexane 1,4-dimethylcyclobutane 1-bromo-2,3-dimethylpentane 16. Define the following terms, give an example a. Organic chemistry: the study of hydrocarbons and their derivatives. b. Hydrocarbon: is a compound that contains only carbon and hydrogen atoms c. Hydrocarbon derivative is a compound that contains carbon and hydrogen and one or more additional elements. d. unsaturated hydrocarbon is a hydrocarbon in which one or more carbon–carbon multiple bonds (double bonds, triple bonds, or both) are present e. Saturated hydrocarbon is a hydrocarbon in which all carbon–carbon bonds are single bonds. f. an alkane : a saturated hydrocarbon in which the carbon atom arrangement is acyclic g. Constitutional isomers are isomers that differ in the connectivity of atoms h. Cycloalkane is a saturated hydrocarbon in which carbon atoms connected to one another in a cyclic (ring) arrangement are present. 5 i. Stereoisomers are isomers that have the same molecular and structural formulas but different orientations of atoms in space j. Cis– trans isomers are isomers that have the same molecular and structural formulas but different orientations of atoms in space because of restricted rotation about bonds. k. Halogenoalkanes is an alkane derivative in which one or more halogen atoms are present l. A substitution reaction is a chemical reaction in which part of a small reacting molecule replaces an atom or a group of atoms on a hydrocarbon or hydrocarbon derivative 17. State physical and chemical properties of alkanes and cycloalkanes 18. Explain why carbon is able to form so many more compounds than most other elements. Carbon atoms have the unique ability to bond to each other in a wide variety of ways that involve long chains of carbon atoms or cyclic arrangements (rings) of carbon atoms. 19. Why it is that alkanes, unlike alkenes, have no geometric isomers? There is free rotation about all carbon–carbon bonds 6