Class Revision on Intro to Organic, Alkanes and Alkenes

Transcription

1 Class Revision on Intro to Organic, Alkanes and Alkenes 2015 Term 1 Week min 110 marks

2 ~ Section A: Multiple Choice Questions Circle the best answer 1. What is the correct name of this compound? CH3 CH3 CH CH2 CH2 CH3 A. 1,3-dimethylbutane B. 2,4-dimethylbutane C. 2-methylbutane D. 2-methylpentane

3 2. The following is a three-dimensional representation of an organic molecule. Which statement is correct? A. The correct IUPAC name of the molecule is 2-methylpentane. B. All the bond angles will be approximately 90. C. One isomer of this molecule is pentane. D. The boiling point of this compound would be higher than that of pentane.

4 3. Which formulas represent butane or its isomer? I. CH 3 (CH 2 ) 2 CH 3 II. CH 3 CH(CH 3 )CH 3 III. (CH 3 ) 3 CH A. I and II only B. I and III only C. II and III only D. I, II and III 4. How many structural isomers are possible with the molecular formula C 6 H 14? A. 4 B. 5 C. 6 D Which compound can exist as optical isomers? A. H 2 NCH 2 COOH B. H 3 CCONH 2 C. H 3 CCHBrI D. HCOOCH 3

5 6. Which amino acid can exist as optical isomers? A. B. C. D. 7. Which compound can exist as optical isomers? A. H 2 NCH 2 COOH B. CH 2 ClCH 2 Cl C. CH 3 CHBrI D. HCOOCH 3

6 8. Which species will show optical activity? A. 1-chloropentane B. 3-chloropentane C. 1-chloro-2-methylpentane D. 2-chloro-2-methylpentane 9. How many chiral carbon atoms are present in a molecule of glucose? A. 1 B. 2 C. 3 D. 4

7 10. Which compound can exist as optical isomers? A. CH 3 CHBrCH 3 B. CH 2 BrCHBrCH 3 C. CH 2 BrCHBrCH 2 Br D. CHBr 2 CHBrCHBr Which species reacts most readily with propane? A. Br 2 B. Br C. Br D. Br Which species is a free radical? A. CH 3 B. C. + CH 3 CH 3 D. :CH 3

8 13. Which statement is correct about the reaction between methane and chlorine? A. It involves heterolytic fission and Cl ions. B. It involves heterolytic fission and Cl radicals. C. It involves homolytic fission and Cl ions. D. It involves homolytic fission and Cl radicals. 14. What is/are the product(s) of the reaction between ethene and hydrogen bromide? A. CH 3 CH 2 Br B. CH 3 CH 2 Br and H 2 C. CH 2 BrCH 2 Br D. CH 3 BrCH 2 Br and H Which compound forms when hydrogen bromide is added to but-2-ene? A. 2-bromobutane B. 2,3-dibromobutane C. 1-bromobutane D. 1,2-dibromobutane

9 16. Which product is formed by the reaction between CH 2 CH 2 and HBr? A. CH 3 CH 2 Br B. CH 2 CHBr C. BrCHCHBr D. CH 3 CHBr What product results from the reaction of CH 2 ==CH 2 with Br 2? A. CHBrCHBr B. CH 2 CHBr C. CH 3 CH 2 Br D. CH 2 BrCH 2 Br ~ Section B: Response Write your answers on a foolscap paper

10 18. (a) Compounds of formula C 4 H 7 Cl exhibits both geometrical and optical isomerism. (i) Explain why C 4 H 7 Cl shows geometrical isomerism (1) (ii) Draw the cis and trans isomers of C 4 H 7 Cl. (iii) Draw the structural formula of C 4 H 7 Cl that shows only optical isomerism. Show the chiral carbon atom with *. (b) Explain why 1,2-dichlorocyclopropane has cis and trans isomers. Draw the structural formulas of the two isomers (3) (Total 8 marks)

11 19. The molecular formula, C 3 H 4 Cl 2 represents several isomeric compounds. Some isomers are cyclic and some are unsaturated. (a) Draw the structures of two cyclic compounds that are structural isomers and state the names of both isomers. (b) Two of the non-cyclic compounds have geometrical isomers. Draw the structures of these compounds and their geometrical isomers. (Total 4 marks) 20. (a) List two characteristics of a homologous series.... (1)

12 (b) Ethanol and ethanoic acid can be distinguished by their melting points. State and explain which of the two compounds will have a higher melting point..... (c) Draw the three isomers containing the alcohol functional group of formula C 4 H 9 OH. (Total 5 marks) 21. Compounds with the molecular formula C 3 H 4 Cl 2 exist as several structural isomers, some of which are cyclic. Some of these structural isomers exist as geometric isomers. (a) Explain why geometrical isomerism is possible in the non-cyclic isomers. (1)

13 (b) Draw the structure of a non-cyclic structural isomer that does not exist as geometric isomers, and explain why geometrical isomerism is not possible in this compound. (c) 1,3-Dichloropropene exists as geometric isomers. Draw and label the structures of its cis and trans isomers. (d) Draw structures to show the two geometric isomers of 1,2-dichlorocyclopropane. (Total 7 marks)

14 22. (a) There are geometrical isomers of the cyclic compound C 4 H 6 Cl 2. Draw the structural formula of two isomers and explain why these two isomers exist. cis-isomer trans-isomer (3) (b) (i) Draw the structural formulas of two isomers of but-2-ene-1,4-dioic acid. (ii) State and explain which isomer will have a lower melting point.

15 (iii) Describe how the two isomers can be distinguished by a chemical test. (c) Consider the following compounds: 1-chloropentane, 2-chloropentane, 3-chloropentane (i) Identify the compound which exhibits optical isomerism and draw the structures of the two isomers. (3) (ii) Describe how these two isomers can be distinguished experimentally. (1) (Total 13 marks)

16 23. This question is about structural isomers and stereoisomers with the molecular formula C 4 H 6 Cl 2. (a) The compound 1,3-dichlorobut-1-ene can be used to illustrate two types of stereoisomerism. For each type of stereoisomerism, draw two structures to show the relationship between the two. two geometrical isomers two optical isomers (4) (b) Explain the term racemic mixture. (1) (c) Outline how the two optical isomers of 1,3-dichlorobut-1-ene can be distinguished from each other and from a racemic mixture. (3)

17 (d) 1,3-dichlorocyclobutane exists as geometrical isomers. Draw the 3-dimensional structures of these isomers. (Total 10 marks) 24. Methylbenzene, C 6 H 5 CH 3, reacts with Cl 2 to form different products depending on the conditions used. For the gas-phase reaction of C 6 H 5 CH 3 and Cl 2 in ultraviolet light, (a) draw a structural formula for the product C 7 H 7 Cl. (1) (b) provide a stepwise mechanism, clearly labelling each step. (5)

18 (c) explain the role of the ultraviolet light..... (1) (Total 7 marks) 25. (a) State two characteristics of a homologous series. (b) Describe a chemical test to distinguish between alkanes and alkenes, giving the result in each case. (3) (Total 5 marks) 26. Ethene, propene and but-2-ene are members of the alkene homologous series. (a) Describe three features of members of a homologous series. (3)

19 (b) State and explain which compound has the highest boiling point. (3) (c) Draw the structural formula and give the name of an alkene containing five carbon atoms. (d) Write an equation for the reaction between but-2-ene and hydrogen bromide, showing the structure of the organic product. State the type of reaction occurring. (3) (e) Propene can be converted to propanoic acid in three steps: step1 step 2 step 3 propene propan-1-ol propanal propanoic acid State the type of reaction occurring in steps 2 and 3 and the reagents needed. Describe how the conditions of the reaction can be altered to obtain the maximum amount of propanal, and in a separate experiment, to obtain the maximum amount of propanoic acid. (5) (f) Identify the strongest type of intermolecular force present in each of the compounds propan-1-ol, propanal and propanoic acid. List these compounds in decreasing order of boiling point. (4) (Total 20 marks) 27. On being reacted separately with HBr, 2-methylbut-1-ene and 2-methylbut-2-ene produce the same major product but different minor products. (a) Draw the structural formula of the major product and explain why it is formed in terms of the stability and structure of the organic intermediate (4)

20 (b) Draw the structural formulas of the two minor products. (Total 6 marks) 28. But-1-ene undergoes an electrophilic addition reaction with iodine chloride, ICl. The major product of this reaction is 2-chloro-1-iodobutane. (a) Show the mechanism of this reaction, using curly arrows to represent the movement of electron pairs. (4) (b) Deduce the name of the minor product of this reaction and explain why only a small amount of it is formed. (4) (Total 8 marks)