CHEM 2312 practice final. Version I

Transcription

1 CEM 2312 practice final Version The following standardized final examination covers the entire introductory year of organic chemistry (CEM 2311 and 2312 at Georgia Tech). The exam consists of 70 multiple choice questions, each with four choices for the correct answer. There is a single correct answer to each question. To most effectively use this as a guide to the final: complete the examination in a single uninterrupted two-hour session without reference to other materials (lock your door, turn off your phone and switch off your computer). Then enter your answers into T-square (there is a link to Practice Final on the WebCT course page). Your exam will be scored (out of 70) and you will get access to the solutions. Question 1

2 Question 1 What is the ground-state electronic configuration of an oxygen atom (oxygen: atomic number 8)? (a) 1s 2 2s p 5 (b) 1s 2 2s 2 2p 4 (c) 1s s p 6 (d) 1s 2 2s 2 2p 2 Question 2 Which of the following is a tertiary alcohol? (a) C 3 C 2 C 3 (b) (C 3 ) 3 C (c) (C 3 ) 2 C (d) C 3 C 2 C 2 Question 3 Which of the following statements is not true regarding resonance structures? (a) All resonance structures must have the same number of electrons (b) Each atom in all of the resonance structures must have a complete shell of valence electrons (c) All resonance structures must have the same arrangement of atoms (d) All resonance structures must be valid Lewis structures Question 4 Which atomic orbitals overlap to form the carbon-carbon σ molecular bonding orbital of ethyne, C C? (a) C2p + C2p (b) Csp + Csp (c) Csp 2 + Csp 2 (d) Csp 3 + Csp 3 Question 5 Which of the following compounds has only 1 and 3 carbon atoms? (a) hexane (b) 2-methylpentane (c) 3-methylpentane (d) 2,3-dimethylbutane Question 6 Which of the following Newman projections does not represent 2-methylhexane? C 3 C(C 3 ) 2 3 C C 2 C 3 C 3 C 2 C 2 C 3 C 2 C 3 C 2 C 3 C 3 Question7 What is the UPAC name for the following compound? (a) cycloheptane (c) bicyclo[5.4]heptane C 2 C 2 C 2 C 3 (b) bicyclo[3.2.0]heptane (d) cyclobutylcyclopentane Question 8 Which of the following is the most stable conformation of cis- 1-isopropyl-3-methylcyclohexane? 3 C C(C 3 ) 2 C 3 C(C 3 ) 2 3 C C(C 3 ) 2 C 3 C(C 3 ) 2 Question 9 Which of the following alkanes has the highest boiling point? (a) 2,3-dimethylbutane (b) 2-methylpentane (c) 3-methylpentane (d) hexane Question 10 Which of the following statements is not true regarding the conformation of substituted cyclohexanes? (a) ring inversion of cyclohexanes between two chair conformations takes place via a boat conformation (b) substituted cyclohexanes are destabilized by 1,3-diaxial interactions (c) the boat conformation of cyclohexane is more stable than the chair conformation (d) the relative amount of two conformations of substituted cyclohexanes can be determined from the difference in strain energy Question 11 What is the approximate dihedral angle between the two chlorine atoms in the diaxial conformation of trans-1,2- dichlorocyclohexane? (a) 0 (b) 60 (c) 120 (d) 180 Question 12 Which of the following undergoes the most exothermic combustion per carbon atom? (a) cyclopropane (b) cyclobutane (c) cyclohexane (d) cycloheptane Question 13 Which of the following is the definition of a pair of enantiomers? (a) A pair of structures that are superposable mirror images of one another (b) A pair of stereoisomers that are non-superposable mirror images of one another (c) A pair of stereoisomers that are not mirror images of one another (d) A pair of stereoisomers that have equal specific rotations

3 Question 14 Which of the following statements is true? (a) All mirror images are enantiomers (b) All molecules that have stereocenter centers are chiral (c) somers that are not superposable on their mirror images are enantiomers (d) Superposable structural isomers are enantiomers Question 15 Which of the following have the S configuration? C 2 C 3 C 2 C 3 Question 19 ow much of the R enantiomer is present in 10 g of a mixture which has an enantiomeric excess of 60% of the R isomer? (a) 2 g (b) 4 g (c) 6 g (d) 8 g Question 20 A solution containing 0.2 g/ml of a pure R enantiomer in a 1 dm polarimeter rotates plane polarized light by +3. What is the specific rotation of the R isomer? (a) (b) +0.6 (c) -0.6 (d) +15 C 3 C 2 C 3 C C 3 C 2 3 C 3 (a) only 1 (b) only 2 (c) only 1 and 2 (d) 1, 2 and 3 C(C 3 ) 2 Question 21 Which of the following is the correct order of decreasing basicity (stronger base > weaker base)? (a) N 3 > MeN 2 > 2 > F (b) MeN 2 > N 3 > Me > C 4 (c) N 3 > Me 3 N > 2 > Me (d) C 3 CNa > Na > NaMe > NaNMe 2 Question 16 Which of the following Newman projections represents meso- 2,3-dibromobutane? 3 C C 3 3 C C C C 3 3 C 3 C Question 17 Which of the following structures represent the same stereoisomer? 4 Question 22 Which of the following terms describes the reactivity of boron tribromide, B 3? (a) ønsted-lowry acid and Lewis acid (b) ønsted-lowry base and Lewis base (c) Lewis acid and not a ønsted-lowry acid (d) Lewis base and not a ønsted-lowry base Question 23 What is the UPAC name of the following compound? C 3 3 C C 3 C 3 (a) bicyclo[6.2]oct-2-ene (c) bicyclo[2.2.2]-2-octene (b) bicyclo[4.4.4]oct-2-ene (d) bicyclo[2.2]-2-octene C 3 C 3 3 (a) only 1 and 2 (b) only 1 and 3 (c) only 2 and 3 (d) 1, 2 and 3 Question B 3 Question 18 ow many stereoisomers of 2-chloro-3-methylbutane, (C 3 ) 2 CCC 3, exist? Na

4 Question 25 C 3 C 3 C Question 29 Which of the following reactions of alkenes is not stereospecific? (a) bromination (treatment with 2 in C 3 ) (b) hydrogenation (treatment with 2 /Pt) (c) acid-catalyzed hydration (treatment with aqueous 2 S 4 ) (d) bromohydrin formation (treatment with 2 / 2 ) C 3 C 3 Question 30 What is the UPAC name of the following compound? Question 26 What type of reactive intermediate is formed in the reaction of an alkene with to give a bromoalkane? (a) carbocation (b) carbanion (c) radical (d) cyclic bromonium ion Question 27 What is (are) the major organic product(s) obtained from the following 2 (a) (R)-1-chloro-3-methyl-2-cyclohexene (b) (S)-1-chloro-3-methyl-2-cyclohexene (c) (R)-3-chloro-1-methylcyclohexene (d) (S)-3-chloro-1-methylcyclohexene Question 31 The reaction of methyl iodide with sodium azide, NaN 3, proceeds by an S N 2 mechanism. What is the effect of doubling the concentration of NaN 3 on the rate of the (a) the rate remains the same (b) the rate decreases by a factor of 2 (c) the rate increases by a factor of 2 (d) the rate increases by a factor of 4 1 (2R,3R)-dibromobutane 2 (2S,3S)-bibromobutane 3 meso-2,3-dibromobutane Question 32 Which of the following alkyl halides undergoes the fastest S N 2 reaction with sodium azide, NaN 3? (a) only 1 (b) only 2 (c) only 3 (d) only 1 and 2 (a) 1-fluorohexane (c) 1-bromohexane (b) 1-chlorohexane (d) 1-iodohexane Question 28 Which of the following alkenes undergoes the most exothermic hydrogenation upon treatment with 2 /Pd? Question 33 2 hν

5 Question 34 n which of the following solvents would the reaction of 1- bromobutane with sodium azide, NaN 3, proceed the fastest? (a) acetic acid (b) ethanol (c) water (d) acetonitrile Question 35 Which of the following statements is not true regarding the S N 2 reaction of (R)-2-bromobutane with sodium cyanide? (a) the reaction proceeds with inversion of configuration (b) the rate is proportional to the concentration of sodium cyanide (c) the rate is proportional to the concentration of (R)-2- bromobutane (d) the rate of the reaction is independent of the identity of the solvent Question 36 Which of the following represents the transition state of the S N 2 reaction between methyl iodide and ammonia? Question 38 What is the best choice of reagent to achieve the following transformation? (a) (c) S 2, pyridine? (b) 2, light (d), 2 Question 39 Cr 3 2 S 4, 2 (a) 1-butene, C 3 C 2 C=C 2 (b) butanal, C 3 C 2 C 2 C (c) butanone, C 3 C 2 CC 3 (d) butanoic acid, C 3 C 2 C 2 C 3 N C 3 N C Question 40 3 N C 3 N C C 3 C 2 C C 2 gs 4 2 S 4 Question 37 Which of the following energy diagrams represents the course of an exothermic S N 1 Question 41 series of reactions? energy energy C 3 C C NaN 2 2 Lindlar catalyst reaction coordinate reaction coordinate energy energy reaction coordinate reaction coordinate

6 Question 42 3 C C 3 Na C 3 C 3 3 C 3 4 C 3 Question 43 What would be the best choice of reagent(s) to perform the following transformation? C 3 Question 48 sequence of reactions? (a) 2-methylbutane (c) 3-methyl-2-butene Mg Et 2 2 (b) 3-methyl-1-butanol (d) 3-methyl-2-butanol Question 49 2 N 3 C (a) peroxyacid (b) 2, 2 ; followed by Na, 2 (c) s 4 ; followed by NaS 3 (d) 2, 2 S 4 C 3 N N 2 N N 2 Question 44 Which of the following compounds gives an infrared spectrum with peaks at 3300 cm -1 (strong, broad peak) and 1640 cm -1 (sharp, weak peak)? Question 50 C 2 2 Zn(Cu) Et 2 C 3 C 3 Question 45 What is the multiplicity of the signal in the 1 NMR spectrum for the protons of ethane? (a) singlet (b) doublet (c) triplet (d) quartet C 2 C 2 Question 46 What is the hydrogen deficiency index for a compound with a molecular formula of C 6 11 N? Question Li Et Question 47 Which of the following compounds gives a 1 NMR spectrum consisting of only two triplets and a singlet? (a) C 3 C(C 3 ) 2 (b) C 3 C 2 C 2 C 2 C 2 C 3 (c) C 3 C 2 C 2 C 3 (d) C 3 C 2 C()C 3 (a) 2-phenyl-2-butanol (c) 3-phenylbutanone (b) 3-phenyl-2-butanol (d) propiophenone, CC 2 C 3

7 Question Ag 2, Na Question 55 Which of the following has the highest K eq for enolization? Question 56 Na, 2 Δ Question 53 Which of the following statements is not true? (a) Reaction of benzophenone with methanol in the presence of acid gives a ketal (b) Reaction of butanal with ethanol in the presence of base gives an acetal (c) Reaction of benzaldehyde with ethanol in the presence of acid gives an acetal (d) Reaction of acetone with methanol in the presence of base gives a hemiketal Question 54 Which ketone-diol undergoes cyclization to form the following ketal?? Question 57 Δ Question 58 What is the approximate range of chemical shift () in the 1 NMR spectrum of the acidic proton of carboxylic acids? (a) 0-2 ppm (c) 7-8 ppm (b) 2-4 ppm (d) ppm

8 Question 59 What is the major organic product of the following sequence of reactions? Question 64 sequence of reactions? S 2 NaCN 1. LiAl RC 3 NaN 3 1. LiAl (a) propylamine (c) butanamide (b) butylamine (d) propyl formamide N 2 N 2 N 2 Question 60 Which of the following is not an intermediate in the ofmann rearrangement of octanamide to give heptanamine? (a) amide anion, RCN - (b) N-bromoamide, RCN (c) isocyanate, R-N=C= (d) imide, RCNCR N 2 Question 61 Which of the following undergoes the most rapid nitration upon treatment with N 3 / 2 S 4? (a) toluene (b) benzene (c) bromobenzene (d) nitrobenzene Question 62 What is the electrophile in the reaction of benzene with acetyl chloride, C 3 C, and Al 3? (a) C 3 C + + (b) C 3 - (c) C 3 C 2 (d) benzene Question 65 Which mechanism accounts for the reaction of 4-bromo-1- nitrobenzene with sodium hydroxide to form 4-nitrophenol? (a) Bimolecular nucleophilic substitution (S N 2) (b) Nucleophilic aromatic substitution by elimination-addition (c) Nucleophilic aromatic substitution by addition-elimination (d) Electrophilic aromatic substitution Question 66 sequence of reactions? C 3 Question 63 Al 3 Zn(g) 1. NaC 2 C 3 C 3 C 2 C 3 C 3 C 3 C 2 C 2 C 2 C 3 C 2 C C 2 C 3 C 2 C 3 C 2 C 2 C 3 C 2 C 2 C 3 C(C 3 ) C 2 C 3 C 2 C 3

9 Question 67 sequence of reactions? 1. NaC 2 C 3 C 3 C 2 1. Na, 2 C 2 C Δ 1 2 Question 68 What is the thermodynamic product obtained from the addition of 1 mole of bromine to 1,3-butadiene? (a) 3,4-dibromo-1-butene (b) (E)-1,4-dibromo-2-butene (c) (Z)-1,4-dibromo-2-butene (d) (Z)-2,3-dibromo-2-butene Question 69 What range of wavelengths corresponds to the ultraviolet region of the electromagnetic spectrum? (a) nm (b) nm (c) μm (d) 2-10 mm Question 70 Δ