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2. Molecular Representations

Intermolecular Forces

2. Molecular Representations

Intermolecular Forces

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How IMFs are related to melting and boiling points.

How IMFs are related to melting and boiling points.

Johnny Betancourt

How hydrogen bonding works.

How hydrogen bonding works.

Johnny Betancourt

How dipole-dipole forces work.

How dipole-dipole forces work.

Johnny Betancourt

How Van der Waals forces work.

How Van der Waals forces work.

Johnny Betancourt

Practice this topic

Multiple Choice

PRACTICE:Which of the following pairs of molecules would have the highest boiling point?

Multiple Choice

PRACTICE:Which of the following pairs of molecules would have the highest boiling point?

Multiple Choice

PRACTICE:Which of the following pairs of molecules would have the highest boiling point?

Multiple Choice

PRACTICE:Which of the following pairs of molecules would have the highest boiling point?

Multiple Choice

Which molecule is nonpolar?

Multiple Choice

Why do branched alkanes have a lower boiling point than linear alkanes with the same molecular formula?

Multiple Choice

Which property of halogens accounts for the observed trends in physical properties such as melting point, boiling point, and dipole moment?

Multiple Choice

Rank the following molecules in order of increasing melting point (lowest mp to highest mp).

Multiple Choice

Predict the molecule in each series with the higher boiling point.

Textbook Question

Predict which compound in each pair has the higher boiling point. Explain your prediction. c. CH3CH2CH2CH2CH3 or (CH3)2CH2CH2CH3 d. CH3CH2CH2CH2CH3 or CH3CH2CH2CH2CH2Cl

Textbook Question

Predict which compound in each pair has the higher boiling point. Explain your prediction. a. CH3CH2OCH3 or CH3CH(OH)CH3 b. CH3CH2CH2CH3 or CH3CH2CH2CH2CH3

Textbook Question

Which of the following pure compounds can form hydrogen bonds? Which can form hydrogen bonds with water? Which ones do you expect to be soluble in water? e. CH3(CH2)3CH3 f. CH2=CH—CH2CH3 g. CH3COCH3 h. CH3CH2COOH

Textbook Question

Draw the hydrogen bonding that takes place between a. two molecules of ethanol. b. two molecules of propylamine.

Textbook Question

For each pair of compounds, circle the compound you expect to have the higher boiling point. Explain your reasoning. a. (CH3)3C—C(CH3)3 or (CH3)2CH—CH2CH2—CH(CH3)2 b. CH3(CH2)6CH3 or CH3(CH2)5CH2OH c. CH3CH2OCH2CH3 or CH3CH2CH2CH2OH

Textbook Question

Predict which compound in each pair has the higher boiling point. Explain your prediction. e.

Textbook Question

Draw the hydrogen bonding that takes place between c. a molecule of dimethyl ether and two molecules of water. d. two molecules of trimethylamine and a molecule of water.

Textbook Question

Diethyl ether and butan-1-ol are isomers, and they have similar solubilities in water. Their boiling points are very different, however. Explain why these two compounds have similar solubility properties but dramatically different boiling points. Diethyl ether bp 35°C 8.4 mL dissolves in 100 mL H2O Butan-1-ol bp 118°C 9.1 mL dissolves in 100 mL H2O

Textbook Question

N-Methylpyrrolidine has a boiling point of 81 °C, and piperidine has a boiling point of 106 °C. b. Tetrahydropyran has a boiling point of 88 °C, and cyclopentanol has a boiling point of 141 °C. These two isomers have a boiling point difference of 53 °C. Explain why the two oxygen-containing isomers have a much larger boiling point difference than the two amine isomers.

Textbook Question

List each set of compounds in order of increasing boiling point. a. hexane, octane, and decane

Textbook Question

Rank the following compounds from highest boiling to lowest boiling:

Textbook Question

Explain the following: a. 1-Hexanol has a higher boiling point than 3-hexanol.

Textbook Question

Explain why c. H2O (100 °C) has a higher boiling point than HF 120 °C2. d. HF 120 °C2 has a higher boiling point than NH3 (-33 °C).

Textbook Question

a. Which of the following compounds forms hydrogen bonds between its molecules? 1. CH3CH2OCH2CH2OH 2. CH3CH2N(CH3)2 3. CH3CH2CH2CH2Br

Textbook Question

In each pair of compounds, which compound has the higher boiling point? Explain your reasoning. c. 2,2,5-trimethylhexane or nonane

Textbook Question

In each pair of compounds, which compound has the higher boiling point? Explain your reasoning. b. nonane or 2-methylheptane

Textbook Question

In each pair of compounds, which compound has the higher boiling point? Explain your reasoning. a. octane or 2,2,3-trimethylpentane

Textbook Question

List each set of compounds in order of increasing boiling point. b. Octane, (CH3)3C—C(CH3)3 and CH3CH2C(CH3)2CH2CH2CH3

Textbook Question

Choose the molecule in each pair you'd expect to have the higher boiling point. Explain your reasoning. (b)

Textbook Question

(•••) Ionic compounds like sodium acetate have a high melting point. Despite this, they are highly soluble in water. Why?

Textbook Question

(•••) Despite methylcyclohexane (98.2 amu) having a higher molecular weight than toluene (92.1 amu), toluene melts at a higher temperature. Why? [Think about how the molecules can interact with each other based on their shape.]

Textbook Question

Choose the molecule in each pair you'd expect to have the higher boiling point. Explain your reasoning. (a) eicosane ( C₂₀H₄₂) vs pentadecane

Textbook Question

Draw a picture of the hydrogen bonding in methanol.

Textbook Question

Which has g. the higher boiling point: 1-bromopentane or 1-chloropentane?

Textbook Question

Which has h. the higher boiling point: diethyl ether or butyl alcohol?

Textbook Question

For each pair of compounds, predict which compound has the higher boiling point. Check [TABLE 6-2] to see if your prediction was right; then explain why that compound has the higher boiling point. c. 1-bromobutane and 1-chlorobutane

Textbook Question

For each pair of compounds, predict which compound has the higher boiling point. Check [TABLE 6-2] to see if your prediction was right; then explain why that compound has the higher boiling point. b. isopropyl chloride and tert-butyl bromide

Textbook Question

For each pair of compounds, predict which compound has the higher boiling point. Check [TABLE 6-2] to see if your prediction was right; then explain why that compound has the higher boiling point. a. isopropyl bromide and n-butyl bromide

Textbook Question

For each pair of compounds, predict which one has the higher molecular dipole moment, and explain your reasoning. c. cis-2,3-dibromobut-2-ene or trans-2,3-dibromobut-2-ene d. cis-1,2-dichlorocyclobutane or trans-1,3-dichlorocyclobutane

Textbook Question

For each pair of compounds, predict the one with a higher boiling point. Which compounds have zero dipole moments? b. cis- or trans-2,3-dichlorobut-2-ene

Textbook Question

For each pair of compounds, predict the one with a higher boiling point. Which compounds have zero dipole moments? a. cis-1,2-dichloroethene or cis-1,2-dibromoethene

Textbook Question

For each pair of compounds, predict the one with a higher boiling point. Which compounds have zero dipole moments? c. cyclohexene or 1,2-dichlorocyclohexene

Textbook Question

Rank the boiling points of the following molecules. Explain your ranking ( 1 = highest bp; 3 = lowest bp ).

Textbook Question

a. Which compound would you expect to have a greater dipole moment, methyl acetate or butanone? b. Which would you expect to have a higher boiling point? Methyl acetate

Textbook Question

Imidazole boils at 257 °C, whereas N-methylimidazole boils at 199 °C. Explain the difference in boiling points.

Textbook Question

Rank the following isomers in order of increasing boiling point, and explain the reasons for your order of ranking.

Textbook Question

Identify the hydrogen bond donors and hydrogen bond acceptors in the following molecules. (a)

Textbook Question

Identify the hydrogen bond donors and hydrogen bond acceptors in the following molecules. (d)

Textbook Question

In each pair, which would you expect to have the higher melting point? (b)

Textbook Question

Identify the hydrogen bond donors and hydrogen bond acceptors in the following molecules.

(b) <IMAGE>

Textbook Question

In each pair, which would you expect to have the higher melting point?

(a) <IMAGE>

Textbook Question

b. Which of the preceding compounds forms hydrogen bonds with a solvent such as ethanol?

1. CH3CH2OCH2CH2OH

2. CH3CH2N(CH3)2

3. CH3CH2CH2CH2Br

Textbook Question

What is the smallest straight-chain alkane that is a liquid at room temperature (which is about 25 °C)?

Textbook Question

Which has

i. the greater density: heptane or octane?

j. the higher boiling point: isopentyl alcohol or isopentylamine?

k. the higher boiling point: hexylamine or dipropylamine?

Textbook Question

b. Which of the preceding compounds forms hydrogen bonds with a solvent such as ethanol?

4. CH3CH2CH2NHCH3

5. CH3CH2CH2COOH

6. CH3CH2CH2CH2F

Textbook Question

Explain why

a. H2O (100 °C) has a higher boiling point than CH3OH 165 °C2.

b. H2O (100 °C) has a higher boiling point than NH3 (-33 °C).

Textbook Question

Which has

a. the higher boiling point: 1-bromopentane or 1-bromohexane?

b. the higher boiling point: pentyl chloride or isopentyl chloride?

Textbook Question

In Table 7.2, what is the smallest alkane, the smallest terminal alkene, and the smallest terminal alkyne that are liquids at room temperature, which is generally taken to be 20 °C to 25 °C?

Textbook Question

N-Methylpyrrolidine has a boiling point of 81 °C, and piperidine has a boiling point of 106 °C.

c. N,N -Dimethylformamide has a boiling point of 150 °C, and N-methylacetamide has a boiling point of 206 °C, for a difference of 56 °C. Explain why these two nitrogen-containing isomers have a much larger boiling point difference than the two amine isomers.

Also explain why these two amides have higher boiling points than any of the other four compounds shown (two amines, an ether, and an alcohol).

<IMAGE> N-methylpyrrolidine, bp 81°C

<IMAGE> tetrahydropyran, bp 88°C

<IMAGE> N,N-dimethylformamide, bp 150°C

<IMAGE> piperidine, bp 106°C

<IMAGE> cyclopentanol, bp 141°C

<IMAGE> N-methylacetamide, bp 206°C

Textbook Question

For each pair of compounds, circle the compound you expect to have the higher boiling point. Explain your reasoning.

d. HOCH2—(CH2)4—CH2OH or (CH3)3CCH(OH)CH3

e. (CH3CH2CH2)2NH or (CH3CH2)3N(f)

f. <IMAGE> or <IMAGE>

Textbook Question

Which of the following pure compounds can form hydrogen bonds? Which can form hydrogen bonds with water? Which ones do you expect to be soluble in water?

a. <CH3CH2)2NH

b. (CH3CH2)3N

c. CH3CH2CH2OH

d. (CH3CH2CH2)2OH

Textbook Question

(••••) Contrary to expectation, the addition of more fluorines to ethane lowers the boiling point. Explain this phenomenon.

<IMAGE>

Textbook Question

(•) In each pair, choose the compound you would expect to have the highest boiling/melting point.

(b) <IMAGE>

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