chapter 5

Organic Chemistry, 8e (Bruice) Chapter 5 Alkenes: Structure, Nomenclature, and an Introduction to Reactivity - Thermodynamics and Kinetics What is the molecular formula of the hydrocarbon that contains 5 carbon atoms, one ring, and one ? bond? Answer: C5H8 Section: 5-1 What is the molecular formula of the hydrocarbon that contains 8 carbon atoms, one ring, and two ? bonds? Answer: C8H12 Section: 5-1 Give the general formula for a cyclic alkene. CnH2n-4 CnH2n-2 CnH2n CnH2n+2 Answer: B Section: 5-1 Give the possibilities in structure for a compound with a formula of C6H10. no rings, no double bonds, no triple bonds one double bond, or one ring two rings, two double bonds, one double bond + one ring, or one triple bond three rings, three double bonds, two double bonds + one ring, one ring + two double bonds, one triple bond + one ring, or one double bond + one ring benzene Answer: C Section: 5-1 Give the degree of unsaturation for benzene. 1 2 3 4 5 Answer: D Section: 5-1 ?-Phellandrene is a hydrocarbon component of eucalyptus oil whose molecular formula is C10H16. A molecule of ?-phellandrene contains 2 ?-bonds. How many rings are in ?- phellandrene? 0 1 2 3 4 Answer: B Section: 5-1 A hydrocarbon with molecular formula C20H34 has what degree of substitution? 2 3 4 5 6 Answer: C Section: 5-1 Muscalure, the sex attractant of the common housefly, is an acyclic alkene that contains 23 carbons. How many hydrogen atoms are in a molecule of muscalure? Answer: 46 Section: 5-1 Provide an acceptable name for the following compound. Answer: 2-ethyl-5,5-dimethyl-1-hexene or 2-ethyl-5,5-dimethylhex-1-ene Section: 5-2 936756258866Provide an acceptable name for the following compound. Answer: 1,6-dibromocyclohexene Section: 5-2 Name the structure. 2-ethyl-1-pentene 2-propyl-1-butene 3-methylenehexane 3-methyl-3-hexene ethyl propyl ethene Answer: A Section: 5-2 Name the structure. 2-methyl-2,4-pentadiene 4-methyl-1,4-pentadiene 2-methylene-4-pentene 4-methylene-2-pentene 2-methyl-1,4-pentadiene Answer: E Section: 5-2 Name the structure. 7-chloro-3-ethyl-4-methyl-3-heptene 1-chloro-5-ethyl-4-methyl-3-heptene 1-chloro-3-pentenyl-2-pentene cis-7-chloro-3-ethyl-4-methyl-3-heptene trans-7-chloro-3-ethyl-4-methyl-3-heptene Answer: A Section: 5-2 Name the structure. 4-chlorocyclohexene 1-chloro-3-cyclohexene 1-chloro-3-cycloheptene 4-chlorocycloheptane 4-chlorocycloheptene Answer: E Section: 5-2 Draw vinyl bromide. Answer: CHBr Section: 5-2 Name the structure. H2CCHCH2I vinyl iodide allyl iodide 1-iodo-2-propene iodomethylethene 2-iodo-1-propene Answer: B Section: 5-2 914400246686What is the common name for the following compound? t-butylene sec-butylene isobutylene butylene methylpropylene Answer: C Section: 5-2 960119209348What is the IUPAC name for the following compound? 2-methyl-1-butene isopentene 2-methybutene 2-ethylpropene 3-methyl-3-butene Answer: A Section: 5-2 What is the IUPAC name for the following compound? 5-methylcyclohexene 4-methylcyclohexene 1-methyl-3-cyclohexene 1-methyl-4-cyclohexene methylcyclohexene Answer: B Section: 5-2 Which of the following is vinyl chloride? CH3CH2Cl CH2CHCH2Cl 959096411519CH2CHCl D) 959089219007E) Answer: C Section: 5-2 Which of the following is an allylic alcohol? CH2CHCH2OCH3 CH2CHCH2CH3 HOCHCHCH2CH3 CH3CHCHCH2OH CH2CHCH2CH2OH Answer: D Section: 5-2 960119220765Provide the IUPAC name for the alkene shown below. Answer: (E)-3,4-dimethyl-3-heptene Section: 5-2 982980257850Provide the proper IUPAC name for the alkene shown below. Answer: 6-bromo-1-methylcyclohexene Section: 5-2 Draw and name the six alkenes which have the molecular formula C5H10. Answer: Section: 5-2 Provide the systematic name of the alkene below. Answer: 2-ethyl-1-hexene Section: 5-2 Provide an acceptable name of the compound below. Answer: 5-isobutyl-1-methylcyclopentene Section: 5-2 Which of the following statements about ethene, C2H4, is incorrect? The H-C-H bond angles are approximately 109.5°. All of the hydrogen atoms are in the same plane. There is a total of five sigma bonds. The carbon atoms are sp2 hybridized. The H-C-H bond angles are approximately 120°. Answer: A Section: 5-3 Which of the following statements about propene, CH2, is correct? All nine atoms lie in the same plane. The compound has a cis and trans isomer. It generally acts as a Lewis acid. There is a total of eight sigma bonds. All the carbon atoms are sp2 hybridized. Answer: D Section: 5-3 Draw the structure of propyl vinyl ether. Answer: Section: 5-2 Give the hybridization, shape, and bond angle for a carbon in ethene. Answer: sp2, trigonal planar, 120° Section: 5-3 Name the structure. cis-3-ethyl-4-hydroxymethyl-hex-3-en-1-yne cis-2,3-diethylpent-2-en-4-yn-1-ol trans-2,3-diethylpent-2-en-4-yn-1-ol cis-3,4-diethylpent-3-en-1-yn-5-ol trans-3,4-diethylpent-3-en-1-yn-5-ol Answer: C Section: 5-2 How many carbons are in the planar double-bond system of 3-methylcyclopentene? 0 1 2 3 4 Answer: C Section: 5-3 Name the structure. cis-4,5-dimethyl-4-hepten-1-ol trans-3,4-dimethyl-3-hepten-7-ol cis-3,4-dimethyl-3-hepten-7-ol trans-4,5-dimethyl-4-hepten-1-ol trans-4,5-dimethyl-4-heptenol Answer: D Section: 5-2 Name the structure. (Z)-4,5-dimethyl-4-hepten-1-ol (E)-4,5-dimethyl-4-hepten-1-ol (E)-3,4-dimethyl-3-hepten-7-ol (Z)-3,4-dimethyl-3-hepten-7-ol (E)-4,5-dimethyl-4-heptenol Answer: B Section: 5-2 Name the structure. (Z)-3-ethyl-2-hydroxymethyl-2-penten-4-ynal (E)-3-ethyl-2-hydroxymethyl-2-penten-4-ynal (Z)-3-ethyl-5-hydroxymethyl-3-penten-1-ynal (E)-3-ethyl-5-hydroxymethyl-3-penten-1-ynal 3-ethyl-5-hydroxymethyl-3-penten-1-ynal Answer: A Section: 5-2 914400261914Name the structure. (2E,4E)-7-chloro-2,4-heptadiene (2Z,4E)-7-chloro-2,4-heptadiene (2Z,4Z)-7-chloro-2,4-heptadiene (2E,4Z)-7-chloro-2,4-heptadiene 7-chloro-2,4-heptadiene Answer: D Section: 5-2 Draw (E)-2-methyl-3-hexen-1-ol. Answer: Section: 5-2 Provide the systematic name of the compound shown below. Make sure to include the E or Z designator if necessary. Answer: (E)-4-ethyl-3-nonene Section: 5-2 Provide the systematic name of the compound shown below. Make sure to include the E or Z designator if necessary. Answer: (Z)-4-fluoro-3-heptene Section: 5-2 Draw the structure of (Z)-1-chloro-2-methyl-2-butene. Answer: Section: 5-2 Which of the following is capable of exhibiting cis-trans isomerism? 1-butene 1-pentene cyclohexene ethene 2-butene Answer: E Section: 5-2 Draw all the possible constitutional isomers of C4H8. Answer: Section: 5-2 Draw the structure of two alkenes with molecular formula C4H8 that do not exhibit cis-trans isomerism. Answer: Section: 5-2 MCAT: 3.2 Which of the following best describes the geometry about the carbon-carbon double bond in the alkene below? 23856951270E Z neither E nor Z Answer: C Section: 4-2 Assign the E or Z configurational label to the following molecule: Answer: The molecule has a Z configuration based on the priority rule established by Cahn- Ingold-Prelog. Section: 4-2 Draw the structure of (Z)-4-ethyl-3-methylheptene. Answer: 91440026860500Section: 5-2 Draw the structure of (Z)-4-ethyl-3,6-dimethyl-3-heptene. Answer: Section: 5-2 Which of the following is not an electrophile? H+ BF3 C) +NO2 Fe+3 CH2CH2 Answer: E Section: 5-5 Which of the following is not a nucleophile? FeBr3 Br- 959103421012NH3 D) E) CH3OCH3 Answer: A Section: 5-5 Draw the curved arrows to show how CH3CH=CHCH3 reacts with HBr to form a carbocation. 939166214445Answer: Section: 5-5 Give the mechanism for the following reaction. Answer: Section: 5-5 Identify the nucleophiles and electrophiles. -OH, BH3, H2O, +CH3, NH3, Br- Answer: nucleophiles: -OH, H2O, NH3, Br- electrophiles: BH3, +CH3 Section: 5-5 Calculate the enthalpy for the following reaction. H-Cl, 103 kcal/mole CH3CH2-H, 101 kcal/mole CH3CH2-Cl, 85 kcal/mole Answer: -21 kcal/mole Section: 5-8 What is the value of ?H in kcal/mole for the reaction shown? (CH3)3C—H + Cl—Cl ? (CH3)3C—Cl + H—Cl Bond energies are: (CH3)3C—H = 91 kcal/mole (CH3)3C—Cl = 78.5 kcal/mole Cl—Cl = 58 kcal/mole H—Cl = 103 kcal/mole A) +32.5 B) -57.5 C) -32.5 D) +57.5 E) -8.5 Answer: C Section: 5-8 How many transition states are present in the following reaction diagram? 3 4 5 2 1 Answer: D Section: 5-12 An increase in which of the following results in a decrease in the rate of the chemical reaction? temperature concentration collision frequency energy of activation fraction of collisions with proper orientation Answer: D Section: 5-11 An increase in which of the following will occur if the reaction temperature is increased? Energy of activation Collision frequency Fraction of collisions with sufficient energy I and II I and III II and III I, II, and III I Answer: C Section: 5-11 What is the activation energy for the reaction B ? A in the following diagram? A B C D E Answer: E Section: 5-10 Which of the following contributes to make ?G° more negative? use of a catalyst a more positive ?H° a more positive ?S° a larger rate constant none of the above Answer: C Section: 5-10 Which of the following correctly describes intermediates and/or transition states? Transition states occur at minima on reaction coordinate diagrams. Both transition states and intermediates occur at maxima on reaction coordinate diagrams. An intermediate is always produced after the rate-determining step of a reaction mechanism. Transition states have partially formed bonds whereas intermediates have fully formed bonds. none of the above Answer: D Section: 5-12 914400219708Which of the following correctly describes the reaction shown? ?H° >0 and ?S° >0 ?H° >0 and ?S <0 ?H° <0 and ?S >0 ?H° <0 and ?S <0 ?H° = ?S = 0 Answer: D Section: 5-6 Under what conditions is ?G° equal to ?H° for a chemical reaction? Answer: Since ?G° = ?H° - T?S°, then ?G° is equal to ?H° when T?S° is zero. Section: 5-6 Consider the conversion of C to D via a one-step mechanism. The activation energy of this conversion is 3 kcal/mol. The energy difference between D and the transition state of the reaction is 7 kcal/mol. Estimate ?H° for the reaction C ? D. Answer: 4 kcal/mol Section: 5-6 Consider the one-step conversion of F to G. Given that the reaction is endergonic by 5 kcal/mol and that the energy difference between G and the transition state for the process is 15 kcal/mol, sketch a reaction-energy profile for this reaction. Make sure to show how the given energy differences are consistent with your sketch. Answer: Section: 5-6 The ?G° for the conversion of "axial" isopropylcyclohexane to "equatorial" isopropylcyclohexane at 298K is -2.1 kcal/mol. Calculate the percentage of isopropylcyclohexane molecules that have the isopropyl substituent in the axial position at this temperature. [R = 1.987 × 10-3 kcal mol-1K-1] Answer: ?G° = -RTlnK -2.1 kcal/mol = -(1.987 × 10-3 kcal mol-1 K-1)(298K)lnK lnK = K = = 34.7 % axial = × 100% = × 100% = 2.8% Section: 5-6 Based on the following energy diagram, which compound, A or C, is formed faster from B? Which is more stable, A or C? Explain. Answer: A is formed faster since the pathway for its formation has the smaller activation energy. C is more stable than A because it has a lower energy. Section: 5-6, 5-10 Answer: K = = 17792701400976Consider the single step interconversion of A and B shown below. How is the equilibrium constant K related to the rate constants k1 and k -1 and to the amounts of A and B present at equilibrium? Section: 5-11 Why do reactions tend to proceed at a faster rate as T increases? Answer: The number of molecular collisions that possesses sufficient energy to overcome the barrier to reaction increases. Section: 5-11 The Arrhenius equation models how the rate constant k increases as both Ea and T increase. increases most when Ea increases and T decreases. increases most when Ea decreases and T increases. increases as both Ea and T decrease. increases as reactant concentrations increase. Answer: C Section: 5-11 Which of the following correctly describes the reaction whose reaction coordinate diagram is shown? endergonic with no transition state exergonic with no transition state endergonic with a transition state exergonic with a transition state endergonic with an intermediate Answer: D Section: 5-6 Given an activation energy of 15 kcal/mol, use the Arrhenius equation to estimate how much faster the reaction will occur if the temperature is increased from 100°C to 120°C. R = 1.987 cal/mol ? K. Answer: The reaction will occur about 2.8 times faster. Section: 5-11 What is the free energy of activation of a one-step reaction? How is it qualitatively related to the rate constant of the reaction? Answer: The free energy of activation of a one-step reaction is the difference in free energy between the transition state and the reactants. As the free energy of activation increases, the rate constant decreases. Section: 5-10 Consider the reaction coordinate diagram shown. Which step has the greatest activation energy? A going to C C going to E E going to G E going to C C going to A Answer: D Section: 5-12 Consider the reaction coordinate diagram shown. Which letters designate intermediates? Answer: C and E Section: 5-12 Consider the reaction coordinate diagram shown. Which step has the greatest rate constant in the forward direction? Answer: Step 3 (E going to G) Section: 5-12 Consider the reaction coordinate diagram shown. What is the rate-determining step in the conversion of A to G? Answer: Step 2 ( C going to E) Section: 5-12 How many degrees of unsaturation are present in a molecule with formula C10H16? 1 2 3 4 5 Answer: C Section: 5-1 959111396025Linalool is a major compound present in the essential oil of coriander. How many degrees of unsaturation are present in this molecule? 2 3 4 5 6 Answer: A Section: 5-1 79) How many degrees of unsaturation are present in this molecule? 1 2 3 4 5 Answer: D Section: 5-1 1005877220031Provide the proper IUPAC name of the following compound Answer: (Z)-3-methylhex-3-ene Section: 5-2 100203025463500Using curved arrows show the movement of electrons in the following reaction. Answer: Section: 5-5 82) Indicate the electrophile and nucleophile in the chemical reaction? Answer: Section: 5-5 A carbocation is a carbon with a negative charge a carbon with a positive charge a carbon with an unpaired electron a carbon with complete octet a carbon with five hydrogens Answer: B Section: 5-5 The rate determining step of a reaction is the slowest step and thus, has highest energy barrier slowest step and thus, has lowest energy barrier fastest step and thus, has highest energy barrier fastest step and thus, has lowest energy barrier none of the above Answer: A Section: 5-12