chapter 19

Organic Chemistry, 7e (Wade) Chapter 19 Amines 1) Which of the following is not an alkaloid? A) cocaine B) mesitylene C) nicotine D) mescaline E) morphine Answer: B Diff: 1 Section: 19.1 2) Sec-Butylamine is the common name of what compound? A) 1-butanamine B) 2-butanamine C) N-methyl-1-propanamine D) N-methyl-2-propanamine E) N-ethylethanamine Answer: B Diff: 2 Section: 19.2 3) Identify the correct systematic name for the following compound. A) N,N-diethyl-5-hydroxycyclohex-1-enamine B) N,N-diethyl-4-hydroxycyclohex-1-en-2-amine C) 3-(diethylamino)cyclohex-3-enol D) 2-(diethylamino)cyclohex-1-en-4-ol Answer: C Diff: 2 Section: 19.2 4) Provide the correct IUPAC name for the following amine. A) 4-(methylamino)-2-methyl-1-pentene B) 2,N-dimethyl-1-penten-4-amine C) 4,N-dimethyl-4-penten-2-amine D) 1,3,N-trimethyl-3-buten-1-amine Answer: C Diff: 3 Section: 19.2 amine takes precedence 5) Provide the structure of N-ethyl-1-butanamine. Answer: CH3CH2CH2CH2NHCH2CH3 lone pair on N Diff: 1 Section: 19.2 6) Draw the structure of N-ethyl-N-methyl-1-hexanamine. Answer: Diff: 2 Section: 19.2 7) Provide the structure of 2,4-dimethylpyridine Answer: Diff: 2 Section: 19.2 8) Provide the IUPAC name for the compound shown below. Answer: 3,3-dimethyl-1-butanamine Diff: 2 Section: 19.2 9) Provide the IUPAC name of (CH3)3CCH2CH2NHCH2CH3. Answer: N-ethyl-3,3-dimethyl-1-butanamine Diff: 2 Section: 19.2 10) Provide the name of (CH3CH2)4N+ Cl-. Answer: tetraethylammonium chloride N+ is ammonia Diff: 2 Section: 19.2 11) Provide the name of the compound shown below. Answer: 6-amino-1-methylcyclohexene alkene takes precedence, must count entire = Diff: 2 Section: 19.2 12) Draw the structure of 3-pentanamine. Answer: Diff: 1 Section: 19.2 13) Provide the systematic name for the compound below. (CH3)4N+Cl- Answer: tetramethylammonium chloride Diff: 1 Section: 19.2 14) Draw the structure of 2,3-dimethyl-2-butanamine Answer: Diff: 2 Section: 19.2 15) Draw the structure of piperidine. Answer: Diff: 2 Section: 19.2 16) Draw the structure of N-propyl-4-methyl-3-octanamine. Answer: Diff: 2 Section: 19.2 17) Provide the name for the compound below. Answer: pyrrole Diff: 2 Section: 19.2 18) Provide the systematic name for the compound below. Answer: 4-aminocyclohexanone Diff: 2 Section: 19.2 19) Provide the systematic name for the compound below. Answer: 2-bromo-N-methylaniline Diff: 2 Section: 19.2 20) Which of the following is a tertiary amine? A) cyclohexylamine B) 3-pentanamine C) methylamine D) N,N-dimethylaniline E) N-ethyl-1-propanamine Answer: D Diff: 1 Section: 19.3 21) Which of the following is a secondary amine? A) cyclohexylamine B) 3-pentanamine C) methylamine D) N,N-dimethylaniline E) N-ethyl-1-propanamine Answer: E 2 alkyl groups are bonded to it Diff: 1 Section: 19.3 22) Which of the following amines is most soluble in water? A) pyrrolidine B) PhNH2 C) (CH3)3N D) (CH3CH2CH2)2NH E) ethylamine Answer: E least carbons Diff: 1 Section: 19.3 23) Which of the following compounds is a 2° amine? A) cyclohexylamine B) t-butylamine C) N-ethylaniline D) N,N-diethylaniline E) N-butylpyridinium bromide Answer: C Diff: 1 Section: 19.3 24) Which of the following amines can be resolved into enantiomers? A) trimethylamine B) 3-pentanamine C) 2-pentanamine D) dimethylammonium chloride E) 4-(dimethylamino) pyridine Answer: C only chiral center Diff: 2 Section: 19.3 25) The nitrogen atom of trimethylamine is __________ hybridized which is reflected in the CNC bond angle of __________. A) sp, 180° B) sp2, 120° C) sp2, 108° D) sp3, 120° E) sp3, 108° Answer: E including lone pair Diff: 2 Section: 19.3 26) The nitrogen's lone pair in pyrrolidine is best described as occupying what type of orbital? A) s B) sp3 C) sp2 D) sp E) p Answer: B not part of aromatic ring Diff: 2 Section: 19.3 27) Which of the following compounds containing a tertiary amine? 1) 2-methyl-2-propanamine 2) N-ethylpyrrolidine 3) N-methylcyclohexylamine 4) 2-(dimethylamino)butanal A) 1 B) 4 C) 3 D) 2 and 4 E) 1 and 3 Answer: D Diff: 2 Section: 19.3 28) Circle all of the following structures that can be resolved into pure enantiomers. No inversion Answer: Diff: 3 Section: 19.3 29) Why can't N-methyl-2-propanamine be resolved into isolable enantiomers even though the compound is chiral? Answer: Enantiomers interconvert rapidly via nitrogen inversion. Lone pair changes faces Diff: 2 Section: 19.3 30) Why can 1,2,2-trimethylaziridine be resolved into enantiomers while N-methyl-1-propranamine cannot? Answer: In 1,2,2-trimethylaziridine the nitrogen atom is contained in a 3-membered ring and cannot readily achieve the sp2 transition state required for nitrogen inversion. Introduction of an sp2 center in a 3-membered ring greatly increases the angle strain. Diff: 3 Section: 19.3 31) Arrange the following compounds in order of increasing boiling point: CH3NHCH2CH3, CH3OCH2CH3, (CH3)3N, and CH3CH2CH2OH. Answer: (CH3)3N < CH3OCH2CH3 < CH3NHCH2CH3 < CH3CH2CH2OH Diff: 2 based on intermolecular forces Section: 19.4 32) Arrange the following compounds in order of increasing boiling point: ethyl methyl ether, 1-propanol, N-methylethanamine, and 1-propanamine. Answer: ethyl methyl ether < N-methylethanamine < 1-propanamine < 1-propanol Diff: 2 Section: 19.4 Primary amine allows for more hydrogen bonding, so stronger than secondary 33) Arrange the following in order of increasing basicity: aniline, p-nitroaniline, p-toluidine, and p-methoxyaniline. Answer: p-nitroaniline < aniline < p-toluidine < p-methoxyaniline Diff: 2 Section: 19.4 look at activators and deactivators 34) Which has the higher boiling point, butan-1-ol or 1-butanamine? Explain briefly. Answer: The O-H bond is more polar than the N-H because oxygen is more electronegative than nitrogen. Thus, alcohols form stronger hydrogen-bonds and have higher boiling points. Diff: 2 Section: 19.4 35) Rank the following compounds in order of increasing boiling point (lowest to highest): triethylamine, cyclohexylamine, di-n-propylamine. Answer: triethylamine < di-n-propylamine < cyclohexylamine Diff: 2 Section: 19.4 lowest= tertiary amine 36) What common names for 1,4-butanediamine and 1,5-pentanediamine are derived from their characteristic pungent odors? Answer: putrescine and cadaverine Diff: 3 Section: 19.4 37) If ethanol has a pKa value of 16, what is the pKb value of the ethoxide anion? Answer: -2 (14-16) Diff: 2 Section: 19.5 38) Provide the product of the reaction shown below. Answer: Diff: 2 Section: 19.5 39) Which of the following amines is most basic? A) aniline B) N-ethylaniline C) N,N-diethylaniline D) piperidine E) pyrrole Answer: D Diff: 2 Section: 19.6 a,b, and c are all pretty equal in terms of basicity, plus all have aromatic rings 40) Which of the following amines is the strongest base? A) cyclohexylamine B) pyrrole C) p-iodoaniline D) piperidine E) imidazole Answer: D only difference b/w A) and D) is primary vs. secondary Diff: 2 Section: 19.6 41) Physostigmine is used in the treatment of glaucoma. Within this structure, the atom indicated by __________ is most basic, while atom __________ is least basic. A) 1 (most basic), 4 (least basic) B) 1 (most basic), 3 (least basic) C) 2 (most basic), 4 (least basic) D) 2 (most basic), 3 (least basic) E) None of the above Answer: A 4 can go through resonance changes making it less basic? Diff: 2 Section: 19.6 42) Since alkyl groups are electron donors, one might conclude that tertiary amines are much more basic than primary amines. Actually, primary and tertiary amines show similar ranges of basicity. Offer an explanation. Answer: While tertiary ammonium cations are stabilized to a greater degree by electron donation, they are larger and thus more poorly solvated. Diff: 2 effects cancel out Section: 19.6 43) Circle the stronger base in the pair below, and briefly explain your choice. Answer: Cyclohexylamine is the stronger base. The lone pair electrons in aniline are delocalized into the adjacent aromatic ? system. Diff: 2 Section: 19.6 44) Circle the stronger base in the pair below, and briefly explain your choice. Answer: Pyrrolidine is the stronger base. Protonation of pyrrole results in loss of aromaticity. Diff: 3 Section: 19.6 45) Circle the stronger base in the pair below, and briefly explain your choice. Answer: Diethylamine is the stronger base. The lone pair electrons in pyridine are in an sp2 orbital which is lower in energy than the sp3 orbital of the lone pair in diethylamine. Diff: 3 lower s character means more basic (sp3 is lower than sp2) Section: 19.6 46) A sample of cyclohexylamine is contaminated with considerable hydrocarbon impurity. How might the sample be purified using a technique based on solubility differences? Answer: Dissolve sample in ether. Wash with dilute HCl solution to convert the amine to the ammonium hydrochloride which is water soluble; hydrocarbon remains in ether. Neutralize the aqueous solution with base to reform the amine and extract with ether. Diff: 2 Section: 19.7 47) In 1H NMR protons on the ?-carbon of amines typically absorb between ?: A) 1.0 and 2.0 ppm B) 2.0 and 3.0 ppm C) 3.0 and 4.0 ppm D) 6.0 and 7.0 ppm E) 9.0 and 10.0 ppm Answer: B Diff: 2 Section: 19.9 48) In the mass spectrum of dipropylamine, the base peak appears at m/z: A) 101 B) 86 C) 72 D) 58 E) none of the above Answer: C Diff: 2 Section: 19.9 49) The ?-carbon atom bonded to the nitrogen of an alkylamine usually appears in what chemical shift (?) range? A) 5-20 B) 30-50 C) 80-100 D) 120-150 E) 180-220 Answer: B Diff: 2 Section: 19.9 50) A three-carbon, nitrogen-containing compound exhibits 3 13C NMR peaks (d 11.2, 27.3, and 44.9). Which of the following compounds best matches this spectral data? A) H2NCH2CH2CH2OH B) (CH3)2CHNH2 C) CH3NHCH2CH3 D) CH3CH2CH2NH2 E) CH3CH2C?N Answer: D Diff: 2 Section: 19.9 51) How might one distinguish a sample of trimethylamine from a sample of n-propylamine using IR spectroscopy? Answer: n-propylamine would show N-H stretches in the IR between 3200 and 3500 cm-1. Diff: 2 due to no N-H bonds for trimethyl…it won’t show up in IR. Spikes depend on hydrogens Section: 19.9 52) How might the presence of an N-H functionally be indicated using NMR spectroscopy? Answer: Like the O-H group, the N-H group undergoes a rapid H exchange reaction with water. Adding D2O to the NMR sample would result in the disappearance of any peaks in the 1H NMR spectrum arising from N-H groups. Diff: 2 Section: 19.9 53) How might one distinguish a sample of n-butylamine from a sample of diethylamine using IR spectroscopy? Answer: Primary amines, like n-butylamine, usually show two spikes in the N-H stretching region of the IR between 3200 and 3500 cm-1 while secondary amines usually show only one. Diff: 3 Section: 19.9 54) When pentanal reacts with ethylamine under conditions of acid catalysis, the major organic product is __________. A) a ketone B) a nitrile C) an imine D) an oxime E) a hydrazone Answer: C Diff: 2 Section: 19.10 55) When CH3CH2CHO reacts with PhNHNH2 under conditions of acid catalysis, the major organic product is __________. A) a ketone B) a nitrile C) an imine D) an oxime E) a hydrazone (type of) Answer: E Diff: 2 Section: 19.10 56) Provide the structure of the major organic product in the reaction below. Answer: Diff: 2 Section: 19.10 57) Provide the structure of the major organic product in the reaction below. Answer: Diff: 2 Section: 19.10 58) When pyrrole undergoes electrophilic aromatic substitution, at which position does substitution occur? A) 2-position B) 3-position C) 4-position Answer: A only one in which positive charge is not on N in sigma complex Diff: 2 Section: 19.11 59) Which of the following chloropyridines readily undergo nucleophilic substitution upon treatment with NaCN? A) 2-chloropyridine B) 3-chloropyridine C) 4-chloropyridine D) both A and C E) both A and B Answer: D 2, 4 are ortho-para directing because it causes a negative charge on N. Diff: 2 Section: 19.11 60) Pyridine typically undergoes electrophilic aromatic substitution __________ rapidly than benzene, and its preferred site of substitution is the __________ - position. A) more, 2 B) more, 3 C) more, 4 D) less, 2 E) less, 3 Answer: E less because N is deactivating…and 3 position is meta. Diff: 2 Section: 19.11 61) When pyridine is treated with a mixture of nitric and sulfuric acids, the major product is: A) 2-nitropyridine B) 3-nitropyridine C) 4-nitropyridine D) 3-aminopyridine E) 4-aminopyridine Answer: B Diff: 3 adds meta position, NO2 is an electrophile Section: 19.11 62) Which compound would react most rapidly with sodium methoxide and heat? A) chlorobenzene B) 2-chloropyridine C) 3-chloropyridine D) 3-chloropyrrole Answer: B Diff: 3 Section: 19.11 63) Devise an efficient method for preparing p-nitrobenzoic acid from toluene. Answer: 1. HNO3, H2SO4 2. Na2Cr2O7, H2SO4 Diff: 1 Section: 19.11 64) Provide the structure of the major organic product in the reaction below. Answer: Diff: 2 adds to meta position because electrophilic substitution Section: 19.11 65) Why are strongly acidic reagents inappropriate when attempting an electrophilic aromatic substitution with aniline? Answer: Acidic reagents protonate the amino group transforming it from an activating group to a deactivating group (NH3+). Diff: 3 Section: 19.11 66) Pyridine does not undergo Friedel-Crafts reactions. Offer an explanation. Answer: The presence of the electronegative atom in the ring deactivates it toward reaction with electrophiles. In fact, the nitrogen lone pair tends to react with electropiles to produce an even further deactivated ring. It should also be noted that the nitrogen lone pair is in an orbital perpendicular to the ring's ? system and could not stabilize the intermediate carbocation in any event. Diff: 3 Section: 19.11 67) Provide the major organic compound in the following reaction. Answer: Diff: 2 Section: 19.12 68) Provide the major organic product of the following reaction. Answer: Diff: 2 Section: 19.12 69) Provide the structure of the major organic product in the reaction below. Answer: exhaustive alkylation results in tetraalkyl amide. Need mild base Diff: 1 Section: 19.12 70) Can 2-methyl-2-butanamine be prepared in good yield from the reaction of ammonia with 2-bromo-2-methylbutane? Why or why not? Answer: No. SN2 reactions do not proceed with tertiary substrates. Diff: 2 Section: 19.12 71) Can 1-hexanamine be prepared in good yield from the reaction of a 1:1 molar ratio of ammonia and 1-bromohexane? Why or why not? Answer: No. Problems with multiple alkylation exist. Need more moles of NH3. Reactivity of bromine Diff: 2 Section: 19.12 72) Which of the following is an intermediate in the mechanism for amide synthesis through acylation of an amine? A) B) C) D) Answer: D Diff: 2 Section: 19.13 73) Provide the major organic product of the following reaction. Answer: Diff: 2 Section: 19.13 74) Draw a structure for the expected product of the following reaction. Answer: Diff: 3 Section: 19.13 75) Provide the structure of the major organic product in the reaction below. Answer: Diff: 2 Section: 19.13 76) Provide a detailed, stepwise mechanism for the reaction of acetyl chloride with n-propylamine. Answer: Diff: 3 Section: 19.13 77) When a 1° amine reacts with an alkyl sulfonyl chloride, the major organic product is __________. A) a tosylhydrazone B) a nitrile C) a sulfoxide D) an oxime E) a sulfonamide Answer: E Diff: 2 Section: 19.14 78) The Hofmann elimination proceeds via a(n) __________ pathway. A) E2 B) E1 C) SN1 D) SN2 E) none of the above Answer: A Diff: 1 Section: 19.15 79) Provide the structure of the major organic product in the reaction below. Answer: Diff: 2 hoffman on least substituted…amine stays on because it was part of ring Section: 19.15 80) Provide the major organic product of the following reaction. Answer: Diff: 2 Section: 19.15 81) Compound A, C9H17N, is an optically inactive alkaloid, containing a tertiary amine that is not located at the bridgehead of the structures fused bicyclic ring system. Exhaustive alkylation of A with methyl iodide, followed by a Hofmann elimination reaction resulted in a racemic mixture of chiral tertiary amine products B, C10H19N. Provide a structure for A and one of the enantiomeric products B. Answer: Diff: 3 Section: 19.15 82) Provide the structure of the major organic product in the reaction below. Answer: Diff: 2 Section: 19.15 83) Provide the structure of the major organic product in the reaction below. Answer: Diff: 3 repeat process twice Section: 19.15 84) Heating a(n) __________ results in a Cope elimination. A) amine oxide B) imine C) enamine D) oxime E) quaternary ammonium salt Answer: A Diff: 1 Section: 19.16 85) Provide the structure of the major organic product in the reaction below. Answer: Diff: 3 Section: 19.16 like ozonanalysis…forms alkene. Hoffman product still favored 86) Provide the structure of the major organic product in the reaction below. Answer: Diff: 2 Section: 19.16 87) Secondary amines react with the nitrosonium ion to generate: A) diazonium salts B) oximes C) N-nitrosoamines D) imines E) anilines Answer: C Diff: 2 Section: 19.17 88) Provide the formula for nitrous acid. Answer: HNO2 Diff: 1 Section: 19.17 89) Provide the structure of the major organic product in the reaction below. Answer: Diff: 1 Section: 19.18 reactant forms nitrosonium ion 90) Devise an efficient method for preparing fluorobenzene from benzene. Answer: 1. HNO3, H2SO4 2. Fe, HCl 3. -OH 4. NaNO2, HCl 5. HBF4 Diff: 2 add Z group last Section: 19.18 91) Provide the major organic compound in the following reaction. Answer: Diff: 2 Section: 19.18 92) Provide the major organic compound in the following reaction. Answer: Diff: 2 Section: 19.18 93) Provide the major organic product of the following reaction. Answer: Diff: 2 Section: 19.18 94) What sequence of reagents can be used to carry out the transformation shown below? Answer: 1. NaNO2, HCl 2. CuBr Diff: 2 Section: 19.18 95) Complete the following reaction by filling in the necessary reagents. Answer: Diff: 3 Section: 19.18 96) Provide the structure of the major organic product in the reaction below. Answer: Diff: 2 Section: 19.18 97) Provide the structure of the major organic product in the reaction below. Answer: Diff: 2 Section: 19.18 98) Devise an efficient method for preparing 4-bromobenzonitrile from benzene. Answer: 1. Br2, FeBr3 though it is a deactivator, still ortho-para directing…add first so Br doesn’t attack amine if amine were added first 2. HNO3, H2SO4 3. Sn, HCl 4. H2SO4, NaNO2 5. CuCN Diff: 2 Section: 19.18 99) Devise an efficient method for preparing m-cresol from m-toluidine. Answer: 1. NaNO2, HCl 2. H3O+ adds –OH Diff: 2 Section: 19.18 100) Devise an efficient method for preparing 3-bromotoluene from toluene. Answer: 1. HNO3, H2SO4 2. Sn, HCl 3. CH3COCl 4. Br2, FeBr3 5. H3O+ 6. H2SO4, NaNO2 7. H3PO2 Diff: 3 Section: 19.18 “efficient maybe” but diff method in book, pg. 908 101) Which of the following amines could be formed by reduction of an amide? 1) benzylamine 2) isopropylamine 3) aniline 4) triethylamine A) 1 B) 3 and 4 C) 1 and 4 D) 2 and 3 E) 1, 3 and 4 Answer: C Diff: 3 Section: 19.19 102) Provide the major organic product of the following reaction. Answer: Diff: 2 Section: 19.19 103) Provide the major organic product of the following reaction. Answer: Diff: 2 Section: 19.19 104) Devise an efficient method for preparing ethylisopropylamine from ethylamine. Answer: CH3COCH3, NaBH3CN (weak reducing agent that won’t reduce carbonyl, but will reduce iminium salt use when forming tertiary amines) Diff: 2 Section: 19.19 105) The final product is a derivative of Amonafide, a drug used to treat breast cancer (J. Med. Chem. 2007, 4122). Complete each step of the synthesis by filling in the necessary reagents. Answer: Diff: 3 Section: 19.20 first step includes formation of tertiary amine (use approp reducing agent). last step involves reduction, then acylation 106) Provide the major organic product of the following reaction. Answer: Diff: 2 Section: 19.21 107) Complete the short synthesis below by providing the necessary reagents. Answer: 1) NaNO2 / HCl 2) CuCN 3) LiAlH4 or H2 / Pd Diff: 3 Section: 19.21 108) Devise an efficient method for preparing 1-pentanamine from 1-chloropentane. Answer: 1. phthalimide anion 2. H2NNH2, heat or 1. NaN3 2. LiAlH4 or H2, Pd Diff: 1 Section: 19.21 109) Devise an efficient method for preparing 2-phenylethanamine from 2-phenylethanol. Answer: 1. PCC 2. H2NOH 3. H2, Ni or LiAlH4 or 1. SOCl2 2. NaN3 3. LiAlH4 or H2, Pd Diff: 1 Section: 19.21 110) Provide the structure of the major organic product in the reaction below. Answer: Diff: 2 Section: 19.21 inversion of configuration because SN2 rxn 111) Provide the structure of the major organic product in the reaction below. Answer: Diff: 2 Section: 19.21 no inversion of config because NOT Sn2. Reduces by hoffan rearrangement 112) Devise an efficient method for preparing 1-pentanamine from but-1-ene. Answer: 1. HBr, ROOR 2. NaCN 3. LiAlH4 Diff: 2 extra carbon added, so not just NaN3, but CN(-) added. Section: 19.21 113 Devise an efficient method for preparing cyclohexylamine from cyclohexylmethanol. Answer: 1. Na2Cr2O7, H2SO4 2. SOCl2 3. NH3 what ends up as NH2 4. Br2, NaOH Diff: 3 Section: 19.21 114) Devise an efficient method for preparing 1,4-diaminobutane from cyclohexene. Answer: 1. KMnO4 2. SOCl2 3. NH3 4. Br2, NaOH hofmann rearrangement Diff: 3 Section: 19.21 14