CHAPTER 7 HW: SUBSTITUTIONS

Transcription

1 CHAPTER 7 HW: SUBSTTUTNS REACTN TYPES 1. assify each reaction as either a substitution, elimination, or addition reaction. Reaction Type NaH H + Na H + (cat.) H CH CH 2 H 2 CH H H + (cat.) H 2 + H 2 TERMNLGY AND PATTERNS 2. dentify the nucleophile and electrophile in each substitution reaction, then give the products of each reaction. H H C + H + 3. Write above the arrow in each reaction the reagent that is needed to convert 1-chlorobutane into each of the following products. H CN C d. CH Page 1

2 REACTN RDER 4. Use the initial rates data for the reaction shown to answer the questions. + H + H A B C nitial [A] nitial [B] Rate of formation of C (mol/l s) 0.2 M 0.2 M M 0.6 M M 0.2 M Using the rate data, what is the overall order of the reaction? What does the order tell you about the reaction mechanism? S N 2 REACTNS: MECHANSM + STERECHEMSTRY 5. Give the organic product of these S N 2 reactions, and draw the curved arrow mechanism. (Note: show separated ions with all ionic species). + NaH KCN + 6. Give the products of these S N 2 reactions, paying attention to stereochemistry. Na acetone (solvent) H 3 C NaSH d. CN - Page 2

3 S N 2 REACTNS: TRANSTN STATES 7. Give the products of this S N 2 reaction. Then draw the energy diagram for the reaction, including the structure of the transition state (with correct geometry). NaH 8. List two factors that contribute to the energy of the S N 2 transition state, which is higher energy than the reactants and products. 9. Draw the transition state for each S N 2 reaction, with the correct geometry. NaSH Page 3

4 S N 2 REACTNS: STERECHEMSTRY 10. Explain the following observations: ptically active 2-bromobutane undergoes racemization upon treatment with a solution of K. ptically active 2-butanol does not racemize upon treatment with a solution of KH. S N 2 REACTNS: LEAVNG GRUPS 11. Explain in detail why reaction C is faster than reaction D. Use appropriate structures with your answer. C CH D CH Explain why product E is formed, not product F, in the reaction below. H 3 C S CH 2 H - CH 2 H not H E F Page 4

5 13. Give the products of each S N 2 reaction. f no reaction is expected, briefly explain why not. S CF 3 CH 2 K H NaCN Na d. S CH3 ( ) 3 CNa e. S NaH S N 2 REACTNS: ALKYL HALDE STRUCTURE 14. NaCN reacts faster in a S N 2 reaction with a primary alkyl halide (e.g. 1-chlorobutane) than with a secondary alkyl halide (e.g. 2-chlorobutane). Explain, using structures. Page 5

6 S N 2 REACTNS: SLVENT 15. Determine if each solvent below is protic or aproti CH 2 H H N H 3 C H 3 C H H 3 C S DMF Acetone Acetic acid DMS Protic or aprotic 16. Protic and aprotic solvents differ in their ability to effectively solvate certain ions. Use drawings of Na solutions in water and acetone (see previous problem for the structure of acetone) to help explain why protic and aprotic solvents Solvate cations essentially equally well. Solvate anions to different extents. 17. Explain why S N 2 reactions are faster in aprotic solvents. Page 6

7 S N 2 REACTNS: NUCLEPHLES 18. n each pair of S N 2 reactions, choose which should occur faster and explain your answer. + F à + NH à + NH 3 à + PH 3 à + à + ( ) 2 CH à d. CH 2 CH 2 + NH 3 à CH 2 CH 2 + KNH 2 à e. S 2 + NH 2 à S 2 + C=NH à f. + NH 2 à + H 2 à S N 2 REACTNS: SUMMARY F VARABLES 19. n each pair of S N 2 reactions, choose which should occur faster. H DMS H H 2 NH 2 acetone NCH 3 acetone H S 2 H 2 SH S 2 H 2 DMF DMF Page 7

8 S N 1 REACTNS: MECHANSM 20. Give the curved arrow mechanism for these S N 1 reactions. H 3 C C + SH - H 2 H + H H + H 21. Explain why two products are formed in this S N 1 reaction. SH SH - S N 1 + SH Page 8

9 22. Draw the energy diagram for this S N 1 reaction, including the structure of the transition state for the rate determining step. CH 2 H CH 2 + H S N 1 REACTNS: SUMMARY F FACTRS 23. n each pair of S N 1 reactions, choose which will occur faster and explain your answer. H 2 H 2 H 2 Na H 2 H 2 d. H H 2 H DMS Page 9

10 24. Explain why a tertiary carbocation is lower in energy than a secondary carbocation. Use an orbital drawing to support your explanation. S N 1 VERSUS S N 2 REACTNS 25. Determine whether each reaction proceeds through an S N 1 or S N 2 mechanism and briefly explain your answer. Then give the major organic products of each reaction, paying attention to stereochemistry where appropriate. f a racemic mixture is expected, draw both products. Reaction Mechanism and why NaN 3 DMS H NaCH 2 d. H 2 e. CF 3 S Na f. K H 2 Page 10

11 26. Give the curved arrow mechanism for each reaction, keeping in mind the mechanism (S N 1 or S N 2). Reaction KH H + K H + H NH 2 HN + H d. H + H (racemic) e. H + H Page 11