Question 1

Examine the IR below and classify the compound.

Accepted Answer

A)  Alcohol 
B)  Aldehyde 
C)  Carboxylic acid 
D)  Ketone 
A)  Alcohol 
B)  Aldehyde 
C)  Carboxylic acid 
D)  Ketone C

Question 2

Why does an alkyne carbon-carbon triple bond vibrate at a higher wavenumber than an alkene carbon-carbon double bond?

Accepted Answer

A)  It is stronger. 
B)  It is weaker. 
C)  It has fewer hydrogens. 
D)  It makes a less stable cation. 
A)  It is stronger. 
B)  It is weaker. 
C)  It has fewer hydrogens. 
D)  It makes a less stable cation. A

Question 3

You observe a compound that exhibits a mass spectrum with peak at 160 and a peak at 162, both of equal intensity. This compound contains:

Accepted Answer

A)  Two chlorine atoms 
B)  One iodine atom 
C)  One bromine atom 
D)  Two bromine atoms 
A)  Two chlorine atoms 
B)  One iodine atom 
C)  One bromine atom 
D)  Two bromine atoms C

Question 4

Which of the following information is primarily obtained from an IR spectrum?

Accepted Answer

A)  Conjugated F1F1F1S1F1F1F10 system present in a compound. 
B)  Functional groups present in a compound. 
C)  Molecular weight of a compound. 
D)  The carbon and hydrogen framework of a compound. 
A)  Conjugated F1F1F1S1F1F1F10 system present in a compound. 
B)  Functional groups present in a compound. 
C)  Molecular weight of a compound. 
D)  The carbon and hydrogen framework of a compound.

Question 5

Which of the following statements is (are) true about a compound that has molecular ion peaks in its mass spectrum at mass 170 and 172, and shows prominent peaks in its IR spectrum at 3150-3000 and 1600 cm-1?

Accepted Answer

A)  The compound is not pure. 
B)  The compound contains a halogen. 
C)  The compound contains an OH group and Csp3-H hybridized bonds. 
D)  Both A (The compound is not pure) and B (The compound contains a halogen) are true statements. 
E)  Both A (The compound is not pure) and C (The compound contains an OH group and Csp3-H hybridized bonds) are true statements. 
A)  The compound is not pure. 
B)  The compound contains a halogen. 
C)  The compound contains an OH group and Csp3-H hybridized bonds. 
D)  Both A (The compound is not pure) and B (The compound contains a halogen) are true statements. 
E)  Both A (The compound is not pure) and C (The compound contains an OH group and Csp3-H hybridized bonds) are true statements.

Question 6

Which of the following statements is (are) true about a compound that has a molecular ion peak in its mass spectrum at mass 104, and shows prominent peaks in its IR spectrum at 3200-2850 cm-1?

Accepted Answer

A)  The compound has a molecular mass of 104. 
B)  The compound contains a C=O group and Csp3-H hybridized bonds. 
C)  The compound contains an OH group and Csp3-H hybridized bonds. 
D)  Both (The compound has a molecular mass of 104) and (The compound contains a C=O group and Csp3-H hybridized bonds) are true statements. 
E)  Both (The compound has a molecular mass of 104) and (The compound contains an OH group and Csp3-H hybridized bonds) are true statements. 
A)  The compound has a molecular mass of 104. 
B)  The compound contains a C=O group and Csp3-H hybridized bonds. 
C)  The compound contains an OH group and Csp3-H hybridized bonds. 
D)  Both (The compound has a molecular mass of 104) and (The compound contains a C=O group and Csp3-H hybridized bonds) are true statements. 
E)  Both (The compound has a molecular mass of 104) and (The compound contains an OH group and Csp3-H hybridized bonds) are true statements.

Question 7

Which of the following structures is consistent with a compound that displays a molecular ion peak at 56 and infrared signals at 2250 and 3600-3200 cm-1?

Accepted Answer

A)  I 
B)  II 
C)  III 
D)  IV 
A)  I 
B)  II 
C)  III 
D)  IV

Question 8

Examine the IR below and classify the compound.

Accepted Answer

A)  Alcohol 
B)  Aldehyde 
C)  Amine 
D)  Ketone 
E)  Carboxylic acid 
A)  Alcohol 
B)  Aldehyde 
C)  Amine 
D)  Ketone 
E)  Carboxylic acid

Question 9

Consider the three organic compounds drawn below. Which of the following statements is (are) true about the IR spectra of I, II, and III?

Accepted Answer

A)  I shows strong absorptions at 2950 cm-1 and 1700 cm-1. 
B)  II shows strong absorptions at 2950 cm-1 and 2250 cm-1. 
C)  III shows strong absorptions at 2950 cm-1 and 3200-3600 cm-1. 
D)  Statements (I shows strong absorptions at 2950 cm-1 and 1700 cm-1) and (III shows strong absorptions at 2950 cm-1 and 3200-3600 cm-1) are true. 
A)  I shows strong absorptions at 2950 cm-1 and 1700 cm-1. 
B)  II shows strong absorptions at 2950 cm-1 and 2250 cm-1. 
C)  III shows strong absorptions at 2950 cm-1 and 3200-3600 cm-1. 
D)  Statements (I shows strong absorptions at 2950 cm-1 and 1700 cm-1) and (III shows strong absorptions at 2950 cm-1 and 3200-3600 cm-1) are true.

Question 10

You are given a bottle of an organic liquid and told it must be either cyclohexane or 1-hexene. Which of the following statements is (are) true about these two compounds?

Accepted Answer

A)  The two compounds can be differentiated by their mass spectra because they will have molecular ion peaks at different m/z. 
B)  1-Hexene will show an absorption at 1650 cm-1 but cyclohexane will not. 
C)  Both cyclohexane and 1-hexene will show C-H absorptions at about 2950 cm-1. 
D)  Statements B (1-Hexene will show an absorption at 1650 cm-1 but cyclohexane will not) and C (Both cyclohexane and 1-hexene will show C-H absorptions at about 2950 cm-1) are both true. 
E)  Statements A (The two compounds can be differentiated by their mass spectra because they will have molecular ions at different masses), B (1-Hexene will show an absorption at 1650 cm-1 but cyclohexane will not), and (Both cyclohexane and 1- hexene will show C-H absorptions at about 2950 cm-1) are all true. 
A)  The two compounds can be differentiated by their mass spectra because they will have molecular ion peaks at different m/z. 
B)  1-Hexene will show an absorption at 1650 cm-1 but cyclohexane will not. 
C)  Both cyclohexane and 1-hexene will show C-H absorptions at about 2950 cm-1. 
D)  Statements B (1-Hexene will show an absorption at 1650 cm-1 but cyclohexane will not) and C (Both cyclohexane and 1-hexene will show C-H absorptions at about 2950 cm-1) are both true. 
E)  Statements A (The two compounds can be differentiated by their mass spectra because they will have molecular ions at different masses), B (1-Hexene will show an absorption at 1650 cm-1 but cyclohexane will not), and (Both cyclohexane and 1- hexene will show C-H absorptions at about 2950 cm-1) are all true.

Question 11

Why is the infrared absorption for the stretching motion of internal alkynes rarely observed?

Accepted Answer

A)  They do not form cations. 
B)  They are too strong. 
C)  Stretching in internal alkynes does not involve a change in dipole moment. 
D)  They do not have hydrogens. 
A)  They do not form cations. 
B)  They are too strong. 
C)  Stretching in internal alkynes does not involve a change in dipole moment. 
D)  They do not have hydrogens.

Question 12

Stronger bonds will be found where in the infrared spectrum?

Accepted Answer

A)  Higher molecular weight 
B)  Lower molecular weight 
C)  Lower wavenumbers 
D)  Higher wavenumbers 
A)  Higher molecular weight 
B)  Lower molecular weight 
C)  Lower wavenumbers 
D)  Higher wavenumbers

Question 13

What type of signal(s) would you observe in the mass and (or) infrared spectrum of the following compound?

Accepted Answer

A)  A signal at 1600 cm-1 
B)  A signal at 3300 cm-1 
C)  A single mass peak at 92 amu 
D)  Two mass peaks at 92 and 94 amu 
A)  A signal at 1600 cm-1 
B)  A signal at 3300 cm-1 
C)  A single mass peak at 92 amu 
D)  Two mass peaks at 92 and 94 amu

Question 14

The functional group region of an infrared spectrum is:

Accepted Answer

A)  Where the cations appear 
B)  Greater than or equal to 1500 cm-1 
C)  Less than 1500 cm-1 
D)  Greater than or equal to 2500 cm-1 
A)  Where the cations appear 
B)  Greater than or equal to 1500 cm-1 
C)  Less than 1500 cm-1 
D)  Greater than or equal to 2500 cm-1

Question 15

Which of the following structures is consistent with a compound that displays a molecular ion peak at 84 and infrared signals at 3000-2850 cm-1 and no signals between 3000-3300 cm-1?

Accepted Answer

A)  I 
B)  II 
C)  III 
D)  IV 
A)  I 
B)  II 
C)  III 
D)  IV

Question 16

A compound X has a molecular ion peak in its mass spectrum at m/z 136. What information does this tell us about X?

Accepted Answer

A)  X has a molecular mass of 136. 
B)  The molecular formula for X is C8H8O2. 
C)  The empirical formula for X is C4H4O. 
D)  Both A (X has a molecular mass of 136) and B (The molecular formula for X is C8H8O2) are true. 
E)  Statements (X has a molecular mass of 136), (The molecular formula for X is C8H8O2), and (The empirical formula for X is C4H4O) are all true. 
A)  X has a molecular mass of 136. 
B)  The molecular formula for X is C8H8O2. 
C)  The empirical formula for X is C4H4O. 
D)  Both A (X has a molecular mass of 136) and B (The molecular formula for X is C8H8O2) are true. 
E)  Statements (X has a molecular mass of 136), (The molecular formula for X is C8H8O2), and (The empirical formula for X is C4H4O) are all true.

Question 17

Which of the following structures is consistent with a compound that displays a molecular ion peak at 103 and infrared signals at 2250 and 1600 cm-1?

Accepted Answer

A)  I 
B)  II 
C)  III 
D)  IV 
A)  I 
B)  II 
C)  III 
D)  IV

Question 18

In an IR spectrum, which of the indicated C-H bonds exhibits a stretching absorption at the largest wave number?

Accepted Answer

A)  I 
B)  II 
C)  III 
D)  IV 
A)  I 
B)  II 
C)  III 
D)  IV

Question 19

The base peak in a mass spectrum corresponds to the most stable fragment. Propose a structure for a compound that is consistent with the following data. 
(a) The molecular ion peak has m/z = 116
(b) The base peak is at m/z = 59.
(c) The compound is composed of C, H and O atoms.
(d) The IR spectrum shows a strong absorbance at 3257 cm-1.

Accepted Answer

A)  I 
B)  II 
C)  III 
D)  IV 
A)  I 
B)  II 
C)  III 
D)  IV

Question 20

Which of the following statements is (are) accurate about the IR spectrum of compounds I, II, and III below?

Accepted Answer

A)  Compound I shows absorptions at 2950 and 1700 cm-1. 
B)  Compound II shows absorptions at 3200-3600 and 1650 cm-1. 
C)  Compound III shows absorptions at 3200-3600 and 2950 cm-1. 
D)  Both (Compound I shows absorptions at 2950 and 1700 cm-1) and (Compound II shows absorptions at 3200-3600 and 1650 cm-1) are true. 
A)  Compound I shows absorptions at 2950 and 1700 cm-1. 
B)  Compound II shows absorptions at 3200-3600 and 1650 cm-1. 
C)  Compound III shows absorptions at 3200-3600 and 2950 cm-1. 
D)  Both (Compound I shows absorptions at 2950 and 1700 cm-1) and (Compound II shows absorptions at 3200-3600 and 1650 cm-1) are true.

Exam 13: Mass Spectrometry and Infrared Spectroscopy

Examine the IR below and classify the compound.

Why does an alkyne carbon-carbon triple bond vibrate at a higher wavenumber than an alkene carbon-carbon double bond?

You observe a compound that exhibits a mass spectrum with peak at 160 and a peak at 162, both of equal intensity. This compound contains:

Which of the following information is primarily obtained from an IR spectrum?

Which of the following statements is (are) true about a compound that has molecular ion peaks in its mass spectrum at mass 170 and 172, and shows prominent peaks in its IR spectrum at 3150-3000 and 1600 cm-1?

Which of the following statements is (are) true about a compound that has a molecular ion peak in its mass spectrum at mass 104, and shows prominent peaks in its IR spectrum at 3200-2850 cm-1?

Which of the following structures is consistent with a compound that displays a molecular ion peak at 56 and infrared signals at 2250 and 3600-3200 cm-1?

Examine the IR below and classify the compound.

Consider the three organic compounds drawn below. Which of the following statements is (are) true about the IR spectra of I, II, and III?

You are given a bottle of an organic liquid and told it must be either cyclohexane or 1-hexene. Which of the following statements is (are) true about these two compounds?

Why is the infrared absorption for the stretching motion of internal alkynes rarely observed?

Stronger bonds will be found where in the infrared spectrum?

What type of signal(s) would you observe in the mass and (or) infrared spectrum of the following compound?

The functional group region of an infrared spectrum is:

Which of the following structures is consistent with a compound that displays a molecular ion peak at 84 and infrared signals at 3000-2850 cm-1 and no signals between 3000-3300 cm-1?

A compound X has a molecular ion peak in its mass spectrum at m/z 136. What information does this tell us about X?

Which of the following structures is consistent with a compound that displays a molecular ion peak at 103 and infrared signals at 2250 and 1600 cm-1?

In an IR spectrum, which of the indicated C-H bonds exhibits a stretching absorption at the largest wave number?

Which of the following statements is (are) accurate about the IR spectrum of compounds I, II, and III below?

Structure and Bonding

Acids and Bases

Introduction to Organic Molecules and Functional Groups

Alkanes

Stereochemistry

Understanding Organic Reactions

Alkyl Halides and Nucleophilic Substitution

Alkyl Halides and Elimination Reactions

Alcohols, Ethers and Epoxides

Alkenes

Alkynes

Oxidation and Reduction

Nuclear Magnetic Resonance Spectroscopy

Radical Reactions

Conjugation, Resonance, and Dienes

Benzene and Aromatic Compounds

Electrophilic Aromatic Substitution

Carboxylic Acids and the Acidity of the O-H Bond

Introduction to Carbonyl Chemistry; Organometallic Reagents; Oxidation and Reduction

Aldehydes and Ketones Nucleophilic Addition

Carboxylic Acids and Derivatives

Substitution Reactions of Carbonyl Compounds at the Alpha-Carbon

Carbonyl Condensation Reactions

Amines

Carbon-Carbon Bond Forming Reactions in Organic Synthesis

Pericyclic Reactions

Carbohydrates

Amino Acids and Proteins

Lipids

Synthetic Polymers

Filters

Which of the following statements is (are) true about a compound that has molecular ion peaks in its mass spectrum at mass 170 and 172, and shows prominent peaks in its IR spectrum at 3150-3000 and 1600 cm^-1?

Which of the following statements is (are) true about a compound that has a molecular ion peak in its mass spectrum at mass 104, and shows prominent peaks in its IR spectrum at 3200-2850 cm^-1?

Which of the following structures is consistent with a compound that displays a molecular ion peak at 56 and infrared signals at 2250 and 3600-3200 cm^-1?

Which of the following structures is consistent with a compound that displays a molecular ion peak at 84 and infrared signals at 3000-2850 cm^-1 and no signals between 3000-3300 cm^-1?

Which of the following structures is consistent with a compound that displays a molecular ion peak at 103 and infrared signals at 2250 and 1600 cm^-1?