Org Chem- Ch 12,13,15

A

Which compound would show a larger than usual M+2 peak in the mass spectrum? A) CH3CH2SCH3 B) (CH3)2CHNH2 C) CH3CH2CO2H D) CH3(CH2)2CH3

D

Which of the following alkyl halides yields the most stable carbocation intermediate during solvolysis in hot ethanol? A) methyl iodide B) (S)-2-bromopentane C) (R)-2-bromopentane D) (S)-3-bromopent-1-ene E) 1-chlorobutane

E

Which of the following compounds absorbs the longest wavelength of UV-visible light? A) (E)-but-2-ene B) (Z)-but-2-ene C) hex-1-ene D) (Z)-1,3-hexadiene E) (E)-1,3,5-hexatriene

C

Which of the following compounds has the most negative heat of hydrogenation? A) 1,4-hexadiene B) 1,5-hexadiene C) 1,2-hexadiene D) 1,3-hexadiene E) hex-1-ene

B

Which of the following compounds is the most reactive dienophile in a Diels-Alder reaction with 1,3-butadiene? A) CH2CHOCH3 B) CH2CHCHO C) CH3CHCHCH3 D) (CH3)2CCH2 E) CH2CH2

A

Which of the following compounds is the most stable? A) (E)-2-methyl-1,3-pentadiene B) 2-methyl-1,2-pentadiene C) (Z)-2-methyl-1,3-pentadiene D) 2-methyl-2,3-pentadiene E) 2-methyl-1,4-pentadiene

D

Which of the following compounds would contain characteristic IR stretches at 3300 and 2200 cm-1? A) CH3CH2CHO B) CH3CH=CHCH2OH C) (CH3)2CHCN D) CH3CH2CH2C≡CH E) CH3C≡CCH2CH3

A

Which of the following does not have a broad absorption with one or more spikes that is centered about 3300 cm-1 in the IR? A) (CH3CH2CH2)3N B) (CH3CH2CH2)2NH C) CH3CH2CH2NH2 D) (CH3)3CNH2 E) (CH2=CHCH2)2NH

B

Which of the following factors influences how intensely a functional group absorbs infrared radiation (large peak vs. small peak)? A) mass of atoms B) dipole moment C) bond strength D) bond length

A

Which of the following fragment peaks would not be present in the mass spectrum of n-hexane? A) 87 B) 71 C) 57 D) 43 E) 29

c

Which of the following functional groups has the most deshielded proton and would be predicted to show an NMR signal that is the farthest downfield? A) benzylic - H B) allylic - H C) aldehyde - H D) aromatic - H E) acetylenic - H

D

Which of the following has a C→H stretch that occurs at the highest stretching frequency? A) hexane B) hex-1-ene C) (E)-hex-2-ene D) hex-1-yne E) hex-2-yne

A

Which of the following molecules has a characteristic broad stretch at 3300 cm-1? A) (CH3)2CHCH2OH B) (CH3)3CH C) (CH3)2CHCCCH3 D) (CH3)2CHCH=CH2 E) (CH3)2CHCO2CH3

C

The presence of which element is indicated by a peak at m/z 127 and a characteristic 127-unit gap in the mass spectrum? A) Br B) Cl C) I D) N E) S

A

The protons marked Ha and Hb in the molecule below are ________. A) chemically equivalent or homotopic B) enantiotopic C) diastereotopic D) endotopic E) none of the above

E

Which of the following molecules has a characteristic stretch at 1750 cm-1? A) (CH3)2CHCH2OH B) (CH3)3CH C) (CH3)2CHCCCH3 D) (CH3)2CHCH=CH2 E) (CH3)2CHCO2CH3

C

Which of the following molecules has a characteristic stretch at 2250 cm-1? A) (CH3)2CHCH2OH B) (CH3)3CH C) (CH3)2CHCCN D) (CH3)2CHCH=CH2 E) (CH3)2CHCO2CH3

C

Which of the following molecules has a characteristic stretch at 3300 cm-1? A) (CH3)2CHCH2NHCH3 B) (CH3)3CH C) (CH3)2CHCCCH3 D) (CH3)2CHCH=CH2 E) (CH3)2CHCO2CH3

B

Which of the following molecules is chiral? A) 1,2-pentadiene B) 2,3-pentadiene C) 2-methyl-2,3-pentadiene D) 2-chloro-4-methyl-2,3-pentadiene E) None of the above molecules is chiral.

1-pentene

Which of the following molecules would be expected to have its C=C stretching frequency at the highest wavenumber: benzene, 1,3-pentadiene, or 1-pentene?

C

Which of the following molecules would have the highest frequency carbonyl stretch? A) (CH3CH2)2CO B) CH3CH2CH2CHO C) CH3CH2CO2CH3 D) CH3CH2CH2CO2H E) CH3CH2CH2CONH2

C

Which of the following most closely matches the CC stretching frequency? A) 3300 B) 3000 C) 2200 D) 1700 E) 1200

D

Which of the following reasons best explains why aromatic protons have a larger chemical shift than protons one carbon removed from a halogen? A) An aromatic ring is more electron withdrawing than a halogen. B) A halogen is more electron withdrawing than an aromatic ring. C) Electron movement induces a magnetic field opposing the external field. D) Electron movement induces a magnetic field reinforcing the external field.

E

Which of the following stretches tends to be the least intense? A) O-H (alcohol) B) O-H (carboxylic acid) C) C-H D) C=O E) C=C

A

Which of the following terms best describes a Diels-Alder reaction? A) a [4+2] cycloaddition B) a [2+2] cycloaddition C) a sigmatropic rearrangement D) a 1,3-dipolar cycloaddition E) a substitution reaction

D

Which of the following would not have a C-H stretch at about 3050 cm-1? A) 1-pentene B) 2-pentene C) 2-methyl-2-pentene D) 2,3-dimethyl-2-pentene E) 2,4-dimethyl-2-pentene

IR

Which region of the electromagnetic spectrum, IR or X-ray, is characterized by waves of lower frequency?

visible

Which region of the electromagnetic spectrum, radio or visible, is characterized by waves of shorter wavelength?

A

Which sequence correctly ranks the regions of the electromagnetic spectrum in order of increasing energy? 1) infrared 2) ultraviolet 3) radio wave A) 3 < 1 < 2 B) 3 < 2 < 1 C) 2 < 1 < 3 D) 1 < 3 < 2

D

Which statement best explains why a carbonyl absorbs infrared radiation at a higher frequency than an alkene absorption? A) Oxygen has a higher molecular mass than carbon. B) A carbonyl bond is more polarized than an alkene bond. C) Resonance delocalization of electrons invokes greater single bond character in a carbonyl bond. D) A carbonyl π bond is much stronger than an alkene π bond.

A

Which substrate would react most rapidly in an SN2 reaction? A) CH3CH2CH=CHCH2Br B) BrCH2CH2CH=CHCH3 C) CH3CHBrCH=CH2CH3 D) CH3CH2CH2CH=CHBr

A

) How many electrons are present in the nonbonding π molecular orbital of the allyl cation? A) 0 B) 1 C) 2 D) 3 E) 4

C

) Which of the following molecules has a characteristic stretch at 2200 cm-1? A) (CH3)2CHCH2OH B) (CH3)3CH C) (CH3)2CHCCCH3 D) (CH3)2CHCH=CH2 E) (CH3)2CHCO2CH3

B

1H nuclei located near electronegative atoms tend to be ________ relative to 1H nuclei which are not. A) shielded B) deshielded C) resonanced D) split E) none of the above

B

An ________ molecular ion peak usually indicates the presence of an odd number of nitrogen atoms in the molecule. A) even B) odd C) intense D) absent

C

A nucleus with an ________ atomic number or an ________ mass number has a nuclear spin that can be observed by the NMR spectrometer. A) even, odd B) odd, even C) odd, odd D) even, even

spectroscopy

Absorption ________ is the measurement of the amount of light absorbed by a compound as a function of the wavelength of light.

B

Absorption of UV-visible energy by a molecule results in: A) vibrational transitions B) electronic transitions C) rotational transitions D) nuclear transitions E) none of the above

D

According to the 1,3-butadiene structure below, which positions would be best to place methoxy groups to yield the most reactive dimethoxy-1,3-butadiene isomer in the Diels-Alder reaction? A) c and d B) a and c C) b and c D) a and d E) a and f

2100 - 2200 cm-1

At approximately what wavenumber does one expect to find the carbon-carbon triple bond stretch in the IR spectrum of an alkyne?

C

At what m/z would the base peak of (E)-2-hexene occur? A) 84 B) 69 C) 55 D) 41 E) 28

E

Describe the number of signals and their splitting in the 1H NMR spectrum of (CH3)2CHOCH3. A) 3 signals: 2 doublets and a septet B) 2 signals: a doublet and a septet C) 3 signals: a doublet, a quartet, and a septet D) 4 signals: 2 doublets, a singlet, and a septet E) 3 signals: a singlet, a doublet, and a septet

A

Electromagnetic radiation in the ________ region is used in 1H NMR spectroscopy. A) radio wave B) ultraviolet C) infrared D) microwave E) X-ray

C

Ethyne (HCCH) does not show IR absorption in the region 2000-2500 cm-1 because: A) CH stretches occur at lower energies. B) CC stretches occur at about 1640 cm-1. C) there is no change in the dipole moment when the CC bond in ethyne stretches. D) there is a change in the dipole moment when the CC bond in ethyne stretches.

A

How many electrons are present in the nonbonding π molecular orbital of the allyl cation? A) 0 B) 1 C) 2 D) 3 E) 4

D

How many electrons populate the π molecular orbitals of the allyl radical? A) 0 B) 1 C) 2 D) 3 E) 4

E

How many molecular orbitals are needed to represent the conjugated pi system of β-carotene? A) 1 B) 10 C) 11 D) 20 E) 22

D

How many nodes, other than the node coincident with the molecular plane, are found in the highest energy π MO of 1,3-butadiene? A) 0 B) 1 C) 2 D) 3 E) none of the above

B

How many nodes, other than the node coincident with the molecular plane, are present in the HOMO of 1,3,5-hexatriene? A) 1 B) 2 C) 3 D) 4 E) 5

C

How many nodes, other than the node coincident with the molecular plane, are present in the LUMO of 1,3,5-hexatriene? A) 1 B) 2 C) 3 D) 4 E) 5

B

How many nuclear spin states are allowed for the 1H nucleus? A) 1 B) 2 C) 3 D) 4 E) 10

E

How many peaks appear in the proton spin decoupled 13 C NMR spectrum of the compound below? A) 1 B) 2 C) 3 D) 4 E) 5

B

How many peaks appear in the proton spin decoupled 13 C NMR spectrum of the compound below? A) 2 B) 3 C) 4 D) 5 E) 6

F

How many unique NMR signals (disregard splitting) would be predicted in the 1H spectrum of the following compound ? A) 2 B) 3 C) 4 D) 5 E) 6 F) 7

B

If a molecule contains 4 elements of unsaturation and signals in the 1H NMR spectrum between δ 7.0 and 8.0 ppm, what structural group is likely to be present? A) a carbonyl group B) an aromatic ring C) a hydroxyl group D) a cyclohexyl ring E) a carbon-carbon triple bond

B

In IR spectroscopy, the CO bond has a ________ frequency than the CN bond because ________. A) higher, an O atom has more mass than an N atom B) lower, an O atom has more mass than an N atom C) higher, an O atom has more electronegativity than an N atom D) lower, an O atom has more electronegativity than an N atom E) higher, an O atom has an even number of neutrons

B

In addition to a carbonyl stretch, which of the following molecules exhibits two characteristic stretches at 2700 and 2800 cm-1? A) (CH3CH2)2CO B) CH3CH2CH2CHO C) CH3CH2CO2CH3 D) CH3CH2CH2CO2H E) CH3CH2CH2COCl

E

In the UV-visible spectrum of (E)-1,3,5-hexatriene, the lowest energy absorption corresponds to a: A) σ to π transition. B) σ to π* transition. C) π to σ* transition. D) σ to σ* transition. E) π to π* transition.

B

In the allyl radical, which π molecular orbital is singly occupied? A) The bonding π molecular orbital. B) The nonbonding π molecular orbital. C) The antibonding π molecular orbital. D) None of the above.

Hertz

In what units are frequency values typically given?

D

Including all possible stereoisomeric forms, how many distinct allylic bromides could be produced when 2-methylpent-1-ene is treated with NBS under irradiation by a sunlamp? A) 2 B) 3 C) 4 D) 5 E) 6

B

One of the following functional groups, sometimes shows a single weak to medium IR adsorption peak in the 2100 to 2250 cm-1 range. Depending on the structure of the compound this peak is sometimes not present, making it easy to misinterpret the spectrum. Which functional group is it? A) carbonyl B) alkyne C) alcohol D) alkene E) carboxylic acid

A

Relative abundance is the unit along the y-axis in a mass spectrum. What are the units on the x-axis? A) mass / charge (m/z) B) mass (m) C) molecular weight (amu) D) frequency (ν)

B

The Diels-Alder reaction is a concerted reaction; this means: A) a mixture of endo and exo products are formed. B) all bond making and bond breaking occurs simultaneously. C) the products contain rings. D) the reaction follows Markovnikov's rule. E) the reaction is highly endothermic.

B

The IR spectrum of a sample contains absorptions at 3050, 2950, and 1620 cm-1. To what class of organic compound does this sample most likely belong? A) alkane B) alkene C) alkyne D) ester E) alcohol

B

The energy difference between the allowed spin states for an 1H nucleus is ________ the strength of the external magnetic field in which it is placed. A) independent of B) directly proportional to C) inversely proportional to D) exponentially related to E) logarithmically related to

directly

The energy of a photon is ________ proportional to its frequency.

inversely

The energy of a photon is ________ proportional to its wavelength.

C

The frequency of the stretching vibration of a bond in IR spectroscopy depends on what two quantities? A) the stiffness of the bond and the electronegativity of the atoms B) the electronegativity of the atoms and the nuclear charges of the atoms C) the masses of the atoms and the stiffness of the bond D) the nuclear charges of the atoms and the atomic radii E) the electronegativity of the atoms and the masses of the atoms

E

The mass spectrum of alcohols often fail to exhibit detectable M peaks but instead show relatively large ________ peaks. A) M+1 B) M+2 C) M-16 D) M-17 E) M-18

A

The mass spectrum of which compound has M+ and M+2 peaks of approximately equal intensity? A) 3-bromopentane B) 3-pentanol C) pentane D) 3-chloropentane E) 3-iodopentane

fingerprint

The region of the IR spectrum which contains the most complex vibrations (600-1400 cm-1) is called the ________ region of the spectrum.

B

Using a 60-MHz spectrometer, the protons in dichloromethane appear at 5.30 ppm. When the same sample is placed in a 100-MHz instrument, where does the signal appear? A) 8.33 B) 5.30 C) 3.18 D) cannot be determined from information given

D

Which compound would be expected to show intense IR absorption at 1715 cm-1? A) (CH3)2CHNH2 B) hex-1-yne C) 2-methylhexane D) (CH3)2CHCO2H

C

Which compound would be expected to show intense IR absorption at 1746 cm-1? A) CH3CH2OCH2CH3 B) CH3CH2CN C) CH3CO2CH2CH3 D) CH3CH2SCH3

A

UV spectroscopy measures the energy required to promote an electron from the ________ molecular orbital to the ________ molecular orbital. A) highest occupied, lowest unoccupied B) lowest occupied, lowest unoccupied C) lowest occupied, highest unoccupied D) highest occupied, highest unoccupied E) None of the above

A

What 1H NMR spectral data is expected for the compound shown? A) 3.8 (1H, septet), 2.1 (3H, s), 1.0 (6H, d) B) 3.8 (1H, septet), 3.3 (3H, s), 1.0 (6H, d) C) 3.3 (3H, s), 2.6 (3H, septet), 1.0 (6H, d) D) 2.6 (1H, septet), 2.1 (3H, s), 1.0 (6H, d)

C

What IR absorption is characteristic of the C-H stretch in alkanes? A) 3500 cm-1 B) 3300 cm-1 C) 2950 cm-1 D) 2250 cm-1 E) 1710 cm-1

E

What IR absorption is characteristic of the C=O stretch in aldehydes? A) 3500 cm-1 B) 3300 cm-1 C) 2950 cm-1 D) 2250 cm-1 E) 1710 cm-1

B

What IR absorption is characteristic of the O-H stretch in alcohols? A) 4000 cm-1 B) 3300 cm-1 C) 2950 cm-1 D) 2250 cm-1 E) 1710 cm-1

D

What IR absorption is characteristic of the carbon-carbon triple bond stretch in alkynes? A) 3500 cm-1 B) 3300 cm-1 C) 2950 cm-1 D) 2250 cm-1 E) 1710 cm-1

B

What IR absorption is characteristic of the terminal C-H stretch in terminal alkynes? A) 3500 cm-1 B) 3300 cm-1 C) 2400 cm-1 D) 2250 cm-1 E) 1710 cm-1

A

What compound exhibits only two signals in its 1H NMR spectrum, a triplet and a quintet? A) BrCH2CH2CH2Br B) BrCH2CH2CH2Cl C) (CH3)2CHCH(CH3)2 D) CH3CH2CH2CH3 E) (CH3)2CHOCH(CH3)2

B

What compound exhibits three singlets in its proton spin decoupled 13C NMR spectrum? A) BrCH2CH2CH2Br B) BrCH2CH2CH2Cl C) (CH3)2CHCH(CH3)2 D) CH3CH2CH2CH3 E) (CH3)2CHOCH(CH3)2

A

What compound has a significant m/z 70 in its mass spectrum? A) 1-pentanol B) 2-butanol C) diethyl ether D) octane E) (E)-2-pentene

C

What descriptive term is applied to the type of diene represented by 1,5-octadiene? A) conjugated diene B) cumulated diene C) isolated diene D) alkynyl diene E) none of the above

A

What descriptive term is applied to the type of diene represented by 2,4-hexadiene? A) conjugated diene B) cumulated diene C) isolated diene D) alkynyl diene E) none of the above

C

What descriptive term is applied to the type of diene shown? A) conjugated diene B) cumulated diene C) isolated diene D) alkynyl diene E) none of the above

C

Which compound would be expected to show intense IR absorption at 2250 cm-1? A) CH3CH2CH2CO2H B) (CH3)2CHCH2OH C) (CH3)2CHCN D) CH3CH2CH2CONH2

A

What effect does conjugation typically have on the frequency at which absorption by CC occurs? A) Conjugation decreases the frequency at which absorption occurs. B) Conjugation increases the frequency at which absorption occurs. C) Conjugation does not affect the frequency at which absorption occurs.

A

What is the hybridization of the central carbon of allene (1,2-propadiene)? A) sp B) sp2 C) sp3 D) p E) none of the above

D

What is the major organic product which results when cycloheptene is irradiated in the presence of N-bromosuccinimide? A) 1-bromocycloheptene B) 2-bromocycloheptene C) 1,2-dibromocycloheptane D) 3-bromocycloheptene E) 4-bromocycloheptene

E

What is the relative area of each peak in a quartet spin-spin splitting pattern? A) 1:2:1 B) 1:2:2:1 C) 1:1:1:1 D) 1:4:4:1 E) 1:3:3:1

E

What m/z characterizes a strong peak in the mass spectrum of cyclopentanol? A) 86 B) 85 C) 84 D) 70 E) 68

E

What multiplicities are observed for the signals in the off-resonance decoupled 13C spectrum of 2-chloropropene? A) 3 singlets B) 2 singlets and a doublet C) a singlet and 2 doublets D) a singlet, a doublet and a triplet E) a singlet, a triplet, and a quartet

C

When (S)-3-bromopent-1-ene is heated in water, which of the following compounds is not produced? A) (S)-pent-1-en-3-ol B) (R)-pent-1-en-3-ol C) pent-4-en-1-ol D) (E)-pent-2-en-1-ol E) (Z)-pent-2-en-1-ol

C

When 1,3-butadiene reacts with CH2CHCN, which of the terms below best describes the product mixture? A) a mixture of two diastereomers B) a single compound C) a racemic mixture D) optically active E) a mixture of bicyclic compounds

E

When a compound contains a sulfur atom, its mass spectrum contains a larger than usual ________ peak. A) M-2 B) M-1 C) M D) M+1 E) M+2

D

When a high energy electron impacts molecule M in the ionization chamber, what type of species is initially produced? A) cation B) anion C) radical D) radical cation E) radical anion

C

Which compound would be expected to show intense IR absorption at 2820, 2710 and 1705 cm-1? A) CH3COCH2CH3 B) PhCOCH3 C) PhCHO D) CH2CHCOCH3

D

Which compound would be expected to show intense IR absorption at 3300 cm-1? A) CH3CCCH3 B) butane C) but-1-ene D) CH3CH2CCH

C

Which compound would be expected to show intense IR absorption at 3363, 3185, 1660 cm-1? A) CH3CH2CH2OH B) (CH3)2CHNH2 C) CH3CH2CONH2 D) but-1-ene

D

Which compound would be expected to show intense IR absorption at 3367, 3282 cm-1? A) but-1-ene B) PhCO2H C) CH3OCH2CH3 D) PhCH2NH2

B

When the relative energies of the s-cis and s-trans conformers of 1,3-butadiene are compared, one finds that: A) the s-cis conformer is lower in energy than the s-trans. B) the s-trans conformer is lower in energy than the s-cis. C) the two conformers are of equal energy.

A

Which bond in the structure below would give rise to the highest absorption frequency in an IR spectrum? A) sp2 C-H B) sp3 C-H C) C-D D) C=C

A

Which compound has a single, weak IR absorption at 3300 cm-1? A) (CH3CH2)2NH B) CH3CH2CH2OH C) CH3CH2CN D) (CH3CH2)2O E) CH3CH=CHCH3

A

Which compound has a strong and broad IR absorption centered at 3400 cm-1? A) 1-butanol B) octane C) diethyl ether D) 2-hexyne E) benzene

E

Which compound has the smallest heat of hydrogenation? A) 5-methyl-1,2-hexadiene B) (E)-5-methyl-1,3-hexadiene C) 5-methyl-1,4-hexadiene D) 2-methyl-1,5-hexadiene E) (E)-2-methyl-2,4-hexadiene

D

Which compound lacks a strong, characteristic IR absorption near 1700 cm-1? A) CH3CH2CO2H B) CH3CH2CHO C) (CH3CH2)2C=O D) (CH3CH2)2O E) H3CH2CO2CH3

A

Which compound would be expected to show intense IR absorption at 1640 cm-1? A) hex-1-ene B) 2-methylheptane C) CH3CH2CH2OH D) CH3CH2COCH3