Homeworks 1, 2, 3 & 4

0

) The formal charge on oxygen in dimethyl ether, CH3OCH3, is: A) +2 B) +1 C) 0 D) -1 E) -2

s

The electron density of __________ orbitals has spherical symmetry.

Answer: TRUE

When filling two or more orbitals of the same energy with electrons, the electrons will go into different orbitals rather than pair up in the same orbital.

CH3OH2+

When methanol (CH3OH) acts as a base, its conjugate acid is __________. A) -CH2OH B) CH3O- C) CH4OH D) CH3OH2+ E) CH4O+

An ether

Anisole, the compound shown below, is an example of __________. A) an ester B) an ether C) an alcohol D) an aldehyde E) a ketone

Isotopes

Atoms with the same number of protons but different numbers of neutrons are called __________.

sp3, <109.5°

Triethylamine [(CH3CH2)3N] is a molecule in which the nitrogen atom is __________ hybridized and the CNC bond angle is __________. A) sp2, >109.5° B) sp2, <109.5° C) sp3, >109.5° D) sp3, <109.5° E) sp, 109.5°

This molecule is a carboxylic acid which contains the carboxyl group as its characteristic functional group.

What is the name of the characteristic functional group found in the molecule CH3CH2COOH? Answer:

London dispersion forces

What type of intermolecular force results from the attraction of coordinated temporary dipoles induced in adjacent molecules? Answer:

Answer: FALSE

When a negatively charged species is most appropriately depicted as a hybrid of several resonance forms, the negative charge present is considered to be rapidly moving between the resonance forms bearing the formal negative charge.

molecular orbitals

When orbitals on different atoms interact, __________ are produced. Answer:

CH3CH2OH is more soluble in water since it can donate a hydrogen bond to water and accept a hydrogen bond from water. CH3OCH3 can only accept a hydrogen bond from water; it does not have hydrogen which can hydrogen bond to water.

Which compound is more soluble in water? Briefly explain your choice. CH3OCH3 or CH3CH2OH Answer:

Amide

Which functional group occurs more than two times in the structure of the HIV protease inhibitor drug called Saquinavir? A) ketone B) carboxylic acid C) amine D) amide E) alkene

both A and C

Which functional groups below indicate the presence of two atoms connected by a triple bond? A) alkyne B) alkene C) nitrile D) ester E) both A and C

van der Waals or London forces

Which intermolecular force is primarily responsible for the interactions among alkane molecules? Answer:

Methansulfonic acid is considerably more acidic. The methanesulfonate ion is much more stable than the propanoate ion. Both of these conjugate bases are stabilized by resonance delocalization of the negative charge, but this delocalization is more extensive in the sulfonate.

Which is more acidic, methanesulfonic acid (CH3SO3H) or propanoic acid (CH3CH2CO2H)? Explain. Answer:

all of the above

Which of the class of organic compound below contains a carbonyl group as a part of its structure? A) aldehyde B) ketone C) carboxylic acid D) ester E) all of the above

Both B and C

Which of the following compounds are covalent compounds? A) KCl B) CF4 C) NH3 D) both A and B E) both B and C

ether

16) Choose the functional group which is not represented in the structure of RU-486. A) alkyne B) alcohol C) ketone D) amine E)

π

A __________ bond results when parallel p orbitals overlap sideways. Answer:

Essentially nonpolar

A carbon-hydrogen bond in ethane (CH3CH3) is best described a __________. A) highly polar B) essentially nonpolar C) ionic D) a multiple bond E) resonance stabilized

Answer: FALSE

A node is a region of high electron density between the two atoms in a covalent bond.

A, B, & C

According to the Lewis definition, which of the following may act as acids? A) NH3 B) HCl C) AlCl3 D) A & B E) A, B, & C

50

According to the following pKa values listed for a set of acids, which would lead to the strongest conjugate base? A) -2 B) 1 C) 7 D) 25 E) 50

wave function

An orbital can be described by its __________, which is the mathematical description of the shape of the electron wave as it oscillates. Answer:

6

An oxygen atom has __________ valence electrons.

sp2, 120°

Boron trifluoride (BF3) is a molecule in which the boron atom is __________ hybridized and the FBF bond angle is __________. Answer:

sp

Choose the correct hybridization for the atom indicated in the molecule below. (CH3)2CHCN ↑ A) sp B) sp2 C) sp3 D) none of the above

sp3

Choose the correct hybridization for the atom indicated in the molecule below. CH3CH2CH2CH3 ↑ A) sp B) sp2 C) sp3 D) none of the above

linear

Choose the term below which best describes the geometry of acetylene (HCCH). A) trigonal bipyramidal B) trigonal C) tetrahedral D) square planar E) linear

The molecular orbital formed has a node between the atoms.

Consider the interaction of two hydrogen 1s atomic orbitals of the same phase. Which of the statements below is an incorrect description of this interaction? A) A sigma bonding molecular orbital is formed. B) The molecular orbital formed is lower in energy than a hydrogen 1s atomic orbital. C) The molecular orbital formed has a node between the atoms. D) The molecular orbital formed is cylindrically symmetric. E) A maximum of two electrons may occupy the molecular orbital formed.

NH3 < H2O < HF

Consider the set of compounds, NH3, HF, and H2O. Rank these compounds in order of increasing acidity and discuss your rationale. Answer:

CH3COO- < CH3O- < NH2-

Consider the species CH3O-, NH2-, and CH3COO-. Rank these ions in order of increasing basicity, and explain your rationale. Answer:

2,3-dimethylbutane < 2-methylpentane < n-hexane

Consider the three isomeric alkanes n-hexane, 2,3-dimethylbutane, and 2-methylpentane. Which of the following correctly lists these compounds in order of increasing boiling point? A) 2,3-dimethylbutane < 2-methylpentane < n-hexane B) 2-methylpentane < n-hexane < 2,3-dimethylbutane C) 2-methylpentane < 2,3-dimethylbutane < n-hexane D) n-hexane < 2-methylpentane < 2,3-dimethylbutane E) n-hexane < 2,3-dimethylbutane < 2-methylpentane

Answer: Electronegativity

Covalent bonds may be polar or nonpolar. What property of the atoms forming a given bond determines this?

8 shape dumbo(?)

Draw the shape of a 2p orbital.

8

The synthetic steroid RU-486 is shown below. How many pi bonds does RU-486 contain? Answer:

60°

For the compound represented by the Newman projection above, what is the dihedral angle between the methyl groups in the conformer that has the smallest molecular dipole moment? A) 0° B) 30° C) 60° D) 120° E) 180°

Two carbon p atomic orbitals overlap side-to-side and in phase to form the p bond that is present. Rotation about the carbon-carbon bond axis requires quite a bit of energy because the p bond is broken as the overlap between the two p orbitals is disrupted.

From a molecular orbital perspective why isn't there relatively free rotation about the carbon-carbon double bond in ethene (CH2=CH2)? Answer:

This carbon-carbon s bond is formed by the head-to-head overlap of two sp3 hybrid orbitals. Rotation about this bond does not disrupt the orbital overlap.

From a molecular orbital perspective, why is there relatively free rotation about the carbon-carbon bond of ethane (CH3CH3)? Answer:

3

How many distinct p orbitals exist in the second electron shell, where n = 2? A) 2 B) 3 C) 4 D) 5 E) 6

2n

If a cyclic alkane hydrocarbon contains n carbon atoms, how many hydrogen atoms must it also contain? A) n B) 2n C) n + 2 D) 2n + 2 E) n - 2

saturated

If a hydrocarbon has no double or triple bonds, it is said to be __________. Answer:

2n + 2

If an acyclic alkane hydrocarbon contains n carbon atoms, how many hydrogen atoms must it also contain? A) n B) 2n C) n + 2 D) 2n + 2 E) n - 2

Answer: FALSE

In a carbon atom, the 2s and 2p orbitals are equal in energy.

A mixture of ionic and covalent

In the compound sodium methoxide (NaOCH3), there is __________ bonding. A) ionic B) polar covalent C) nonpolar covalent D) a mixture of ionic and covalent E) resonance stabilized

CH3COO-, nucleophile O2S(OCH3)2, electrophile

In the reaction below, label each reactant as a nucleophile or an electrophile. CH3COO- + O2S(OCH3)2 → CH3COOCH3 + CH3SO4- Answer:

BH3, electrophile CH3SCH3, nucleophile

In the reaction below, label each reactant as a nucleophile or an electrophile. + - BH3 + CH3SCH3 → H3B - S(CH3)2 Answer:

Methanesulfonic acid is the stronger acid. The lower the pKa, the stronger the acid. A lower pKa is associated with a larger Ka which signifies greater dissociation. The large relative difference in acidity in this case can be most easily seen by gauging the relative basicities of the conjugate bases. The weaker the base, the stronger the corresponding conjugate acid. Methanesulfonate, CH3SO3-, is considerably stabilized by resonance delocalization which is not found in ethoxide, CH3CH2O-. This effect greatly reduces the basicity of methanesulfonate relative to ethoxide.

Methanesulfonic acid, CH3SO3H, has a pKa of -7 while ethanol, CH3CH2OH, has a pKa of 15.9. Which is the stronger acid and what accounts for this large difference in relative acidity? Answer:

Degenerate

Orbitals which are equal in energy are referred to as __________. A) degenerate B) polar C) nodes D) filled E) nonpolar

C16H34

Predict the molecular formula of 4-ethyl-5,5-dimethyldodecane. Answer:

4-propylheptane

Provide an acceptable name for (CH3CH2CH2)3CH. Answer:

hexane or n-hexane

Provide an acceptable name for the alkane shown below. CH3CH2CH2CH2CH2CH3 Answer:

The hybridization of the oxygen atom is sp2 and the OCH bond angle is approximately 120°.

Provide the hybridization of oxygen in acetaldehyde (CH3CHO) and estimate the OCH bond angle. Answer:

(CH3)3N + H2O

Provide the products of the following acid-base reaction. (CH3)3NH+ + HO-→ Answer:

CH4 < NH3 < CH3OH < HCl

Rank the following compounds in order of increasing acidity: CH3OH, HCl, NH3, and CH4. Answer:

H2O < NH3 < CH3O- < H2N-

Rank the following compounds in order of increasing basicity: CH3O-, H2N-, H2O, and NH3. Answer:

n-alkanes

Straight-chain alkanes are also called __________. Answer:

180°

The HCN bond angle in hydrogen cyanide (HCN) is __________. Answer:

Pauli exclusion principle

The __________ tells us that each orbital can hold a maximum of 2 electrons. A) aufbau principle B) Pauli exclusion principle C) Hund's rule principle D) LeChatelier principle E) uncertainty principle 34) Draw a line-angle formula for (CH3)2CHCH2CH2NH2.

1s22s22p1

The atomic number of boron is 5. The correct electronic configuration of boron is: A) 1s22s3 B) 1s22p3 C) 1s22s22p1 D) 2s22p3 E) 1s22s23s1

Slightly positive

The compound methylamine, CH3NH2, contains a C-N bond. In this bond, which of the following best describes the charge on the carbon atom? A) +1 B) slightly positive C) uncharged D) slightly negative E) -1

Up, right

The electronegativity of elements on the periodic table increases going __________ a column and to the __________ in each row. A) up, right B) up, left C) down, right D) down, left

Sodium

The element with the electronic configuration 1s22s22p63s1 is __________.

an electron-pair acceptor

The hydroxide ion (HO-) cannot function well as which of the following? A) a Bronsted-Lowry base B) a Lewis base C) a nucleophile D) an electron-pair acceptor E) a proton acceptor

The molecule can be classified as an aldehyde.

The structure of vitamin C is shown below. Which one of the following statements concerning this structure is not correct? A) The molecule contains 2 pi bonds. B) The molecule contains 1 sp2 hybridized oxygen atom. C) The molecule contains 3 sp2 hybridized carbon atoms. D) The molecule can be classified as an aldehyde. E) The molecule contains more than one hydroxyl group.

cyclohexane < cyclopentane < cyclobutane < cyclopropane

Which of the following correctly ranks the cycloalkanes in order of increasing ring strain per methylene? A) cyclopropane < cyclobutane < cyclohexane < cyclopentane B) cyclohexane < cyclopentane < cyclobutane < cyclopropane C) cyclohexane < cyclobutane < cyclopentane < cyclopropane D) cyclopentane < cyclopropane < cyclobutane < cyclohexane E) cyclopropane < cyclopentane < cyclobutane < cyclohexane

cis 1,3-difluorocyclohexane

Which of the following difluorocyclohexane isomers has the greatest molecular dipole in its least stable chair conformation? A) cis 1,2-difluorocyclohexane B) trans 1,2-difluorocyclohexane C) cis 1,3-difluorocyclohexane D) trans 1,3-difluorocyclohexane

Ether

Which of the following does not contain a carbonyl group? A) aldehyde B) ketone C) carboxylic acid D) ester E) ether

Ether

Which of the following functional groups does not have at least one sp2 hybridized carbon atom as a constituent of the group? A) carboxylic acid B) alkene C) aldehyde D) ether E) ester

Ketone

Which of the following functional groups is not present in the HIV protease inhibitor drug called Saquinavir? A) alcohol B) amide C) aromatic D) amine E) ketone

H2N- > CH3COO-

Which of the following pairs of bases lists the stronger base first? A) I- > Cl- B) H2O > HO- C) HO- > H2N- D) CH3COO- > HO- E) H2N- > CH3COO-

Most of the electron density in a π molecular orbital is centered above and below the internuclear axis.

Which of the following statements about π molecular orbitals is/are correct? A) π molecular orbitals are cylindrically symmetric. B) Most of the electron density in a π molecular orbital is centered above and below the internuclear axis. C) When two atoms are connected by a double bond, both of these bonds are π bonds. D) Both statements B and C are correct. E) Statements A, B, and C are all correct.

The methyl group at C-3 is equatorial.

Which of the following statements is a correct description of the most stable conformation of 1,1,3-trimethylcyclohexane? A) The methyl group at C-3 is equatorial. B) C-1 is a tertiary carbon and C-3 is a primary carbon. C) C-1 is a quaternary carbon and C-3 is a secondary carbon. D) C-1 is a tertiary carbon and C-3 is a secondary carbon. E) Both methyl groups at C-1 are equatorial.

Lewis acid

Which of the following terms comes closest to describing an electrophile? A) anion B) Lewis base C) Lewis acid D) nucleophile E) nonpolar

B and C only

Which of the functional groups below contain a hydroxyl group as a part of their structure? A) aldehyde B) alcohol C) carboxylic acid D) amine E) B and C only

CH3CH2NHCH3

Which of the molecules below can be properly called an amine? A) CH3CN B) CH3COOH C) CH3CH2CH2OH D) CH3CH2NHCH3 E) CH3CH2CH2NO2

(CH3CH2)2CHOH

Which of the molecules below can hydrogen bond to another of the same compound? A) CH3CH2OCH2CH3 B) CH3CH2COOCH3 C) (CH3CH2)2CHOH D) CH3CH2COCH2CH3 E) all of the above

CH3CH2CH2NH2 has the higher boiling point since it is capable of intermolecular hydrogen bonding.

Which of the molecules below has the higher boiling point? Briefly explain your choice. (CH3)3N or CH3CH2CH2NH2 Answer:

CH3CH2CH2OH has the higher boiling point since it is capable of intermolecular hydrogen bonding.

Which of the molecules below has the higher boiling point? Briefly explain your choice. CH3CH2CH2OH or CH3CH2OCH3 Answer:

CH3COOCH3

Which of the molecules below is an ester? A) CH3CH2CH(CH3)2 B) CH3OCH2CH2CH3 C) CH3COOH D) CH3COOCH3 E) HC≡CCH3

both A and C

Which of the statements below accurately describe(s) alkanes? A) Alkanes are hydrocarbons that contain only single bonds. B) Alkanes belong to the class of unsaturated hydrocarbons. C) Alkanes are the simplest and least reactive class of organic compounds. D) both A and B E) both A and C

The two chair conformations are equal in energy.

Which of the statements below correctly describes the chair conformations of trans-1,3-diethylcyclohexane. A) The two chair conformations are equal in energy. B) The higher energy chair conformation contains two axial ethyl groups. C) The higher energy chair conformation contains two equatorial ethyl groups. D) The lower energy chair conformation contains two axial ethyl groups. E) The lower energy chair conformation contains two equatorial ethyl groups.

The higher energy chair conformation contains two axial methyl groups.

Which of the statements below correctly describes the chair conformations of trans-1,4-dimethylcyclohexane? A) The two chair conformations are of equal energy. B) The higher energy chair conformation contains one axial methyl group and one equatorial methyl group. C) The lower energy chair conformation contains one axial methyl group and one equatorial methyl group. D) The higher energy chair conformation contains two axial methyl groups. E) The lower energy chair conformation contains two axial methyl groups.

CH3CCl3

Which one of the molecules shown below has a net molecular dipole moment? A) CCl4 B) CO2 C) CH3CCl3 D) BeCl2

Alkanes are nonpolar and as such they do not dissolve to any appreciable extent in water.

Why are alkanes described as hydrophobic? Answer:

Answer: TRUE

Within a given row of the periodic table, electronegativity typically increases left to right across the row.

Trifluoromethanesulfonic acid is a stronger acid. Compare the strengths of the conjugate bases and remember that the weaker the base, the stronger the conjugate acid. Both bases are stabilized by resonance, but in the case of the trifluoro derivative, the presence of the highly electronegative fluorine atoms serves to delocalize the negative charge to an even greater extent. This additional delocalization makes trifluoromethanesulfonate a weaker base.

Would you predict trifluoromethanesulfonic acid, CF3SO3H, to be a stronger or weaker acid than methanesulfonic acid, CH3SO3H? Explain your reasoning. Answer:

HCN + NaOH → NaCN + H2O

Write a completed equation for the acid-base pair shown below. HCN + NaOH → Answer:

HCO2H + -NH2 → HCO2- + NH3

Write a completed equation for the acid-base pair shown below. HCO2H + -NH2 → Answer: