1 CH241 Structure & Bonding

1. Structure and Bonding1. Structure and Bonding Why this chapter?• Review ideas from general chemistry: atoms, bonds, molecular geometry

What is Organic What is Organic Chemistry?Chemistry?Living things are made of organic

chemicalsProteins that make up hairDNA, controls genetic make-upFoods, medicinesExamine structures below

2

Origins of Organic Origins of Organic ChemistryChemistryFoundations of organic chemistry from mid-

1700’s.

Compounds obtained from plants, animals hard to isolate, and purify.

Compounds also decomposed more easily.

Torben Bergman (1770) first to make distinction between organic and inorganic chemistry.

It was thought that organic compounds must contain some “vital force” because they were from living sources.

3

Because of “Vital force”, it was thought that organic compounds could not be synthesized in laboratory like inorganic compounds.

1816, Chervrut showed that not to be the case, he could prepare soap from animal fat and an alkali

1828, Wholer showed that it was possible to convert inorganic salt ammonium cyanate into organic substance “urea”

4

• Organic chemistry is study of carbon compounds.

• Why is it so special?- 90% of more than 30 million

chemical compounds contain carbon.- Examination of carbon in periodic

chart answers some of these questions.

- Carbon is group 4A element, it can share 4 valence electrons and form 4 covalent bonds.

5

1.1 Atomic Structure 1.1 Atomic Structure

Structure of an atom◦ Positively charged nucleus (very dense, protons and neutrons) and small (10-15 m)

◦ Negatively charged electrons are in a cloud (10-10 m) around nucleus Diameter is about 2 10-10 m (200 picometers (pm)) [the unit angstrom (Å) is 10-10 m = 100 pm]

6

A A = Atomic mass

= # p# p ++ # n# n

The Atomic SymbolThe Atomic Symbol

XAA

ZZ

CC

##

ZZ = Atomic #

# p = # e

C C = Charge = + or - values

## = Number of atoms in a formula.


X1212

66

A A = Atomic mass = # protons# protons ++ # neutrons# neutrons

ZZ = Atomic number

= # protons# protons = # electrons# electrons

++++

++++

++ ++

--

--

------

--

6 6


CC1212

66

A A = Atomic mass = # protons# protons ++ # neutrons# neutrons

ZZ = Atomic number

= # protons# protons = # electrons# electrons

++++

++++

++ ++

--

--

------

--


Na2323

1111

1+1+

A A = Atomic mass = p + n = 23

ZZ = Atomic # = p = 11

C C = Charge = +1

## = 1 atom in formula.

SodiumSodium

11 12

Ag107.87107.87

Silver47 Atomic number

Name of the element

Elemental Symbol

Atomic mass (weight)

Atomic weightAtomic weight = The averageaverage, relative mass of an atom in an element.

Why is the atomic weight on the tables not a whole #?

Isotopes of HydrogenIsotopes of HydrogenIsotopes =Isotopes = Atoms of the same

element but having different masses.11

21

31

++

H H H

--

++

--++

--

Protium99.99%99.99%

Deuterium0.01%0.01%

TritiumTrace %Trace %

Isotopes of HydrogenIsotopes of HydrogenIsotopes =Isotopes = Atoms of the same

element but having different masses.11

21

31

++

H H H

--

++

--++

--

Average Atomic weightAverage Atomic weight of Hydrogen = 1.00794 amu1.00794 amu

++++

++++++ ++

Isotopes of CarbonIsotopes of Carbon

--

Average Atomic weightAverage Atomic weight of C= 12.011 amu12.011 amu

98.89%98.89%

CC661212 CC66

1313CC66

1414

++++

++++++ ++

--

1.11%1.11%

++++

++++++ ++

--

Trace %Trace %

--

----

---- --

--

-- --

--

--

--

----

--

Radioactive IsotopesRadioactive Isotopes

CC661414

++++

++++++ ++

--

--

--

----

--

31 H

++

--

Nucleus is unstableSo falls apart (decays)

Giving radioactive particles

H-3H-3 C-14C-14

Electronic arrangementElectronic arrangement

A new layer isadded for each row or period in the table.

Electron arrangementElectron arrangement

2288

18183232

Electronsfill layers

around nucleusLow High

Shells = Energy levelsShells = Energy levels

24241212MgMg

1111HH

7733LiLi

4422HeHe

IA IIA

9944BeBe

2, 12, 1 2, 22, 2

111155 BB

1111HH

7733LiLi

IA IIA IIIA

9944BeBe

2, 12, 1 2, 22, 2 2, 32, 3

111155 BB

121266 CC

131377 NN

IIIA IVA VA

2, 32, 3 2, 42, 4 2, 52, 5

9944BeBe

1111HH

7733LiLi

4422HeHe

20201010 NeNe

23231111 NaNa

24241212MgMg 4040

1818ArAr

IA IIA VIIIA

2, 12, 1 2, 22, 2

2, 8, 12, 8, 1 2, 8, 22, 8, 2

2, 82, 8

2, 8, 82, 8, 8

33

24241212MgMg

1111HH

7733LiLi

23231111 NaNa

9944BeBe 1111

55 BB

27271313AlAl

Valence electronsValence electronsWhere most chemical

Reactions occur.

11

22

2, 12, 1 2, 22, 2

2, 8, 12, 8, 1 2, 8, 22, 8, 2

2, 32, 3

2, 8, 32, 8, 3

1111HH

7733LiLi

4422HeHe

9944BeBe 2020

1010 NeNe

23231111 NaNa

24241212MgMg 4040

1818ArAr

8811

22

2, 12, 1 2, 22, 2 2, 82, 8

2, 8, 12, 8, 1 2, 8, 22, 8, 2 2, 8, 82, 8, 8

Octet RuleOctet Rule

The octet ruleThe octet ruleAtoms are most stable if they have a filled or empty outer layer of electrons.Except for H and He, a filled layer contains 8 electrons - an octet.

Atoms gain, lose or share electrons to make a filled or empty outer layer.

Atoms gain, lose or share electrons based on what is easiest.

1.2 Atomic Structure: 1.2 Atomic Structure: OrbitalsOrbitals

Quantum mechanics: describes electron energies and locations by a wave equation◦Wave function solution of wave equation ◦Each wave function is an orbital,

26

OrbitalsOrbitals

p (3)s (1) d (5) f (7)

A plot of 2 describes where electron most likely to be

Electron cloud has no specific boundary so we show most probable area

An f orbital

4 different kinds of orbitals for e-s s and p orbitals most important in organic &

biochem

Orbitals and ShellsOrbitals and ShellsOrbitals are grouped in shells of increasing size and energyDifferent shells contain different numbers and kinds of orbitalsEach orbital can be occupied by two electrons

28

Orbitals and ShellsOrbitals and Shells1st shell contains one s orbital, denoted 1s, holds

2 e-s2nd shell contains one s orbital (2s) and three p

orbitals (2p), 8 electrons3rd shell contains an s orbital (3s), three p orbitals

(3p), and five d orbitals (3d), 18 electrons

29

p-Orbitalsp-Orbitals In each shell there are three

perpendicular p orbitals, px, py, and pz, of equal energy

Lobes of a p orbital are separated by region of zero electron density, a node

30

1.3 Atomic Structure: Electron 1.3 Atomic Structure: Electron ConfigurationsConfigurations

Ground-state electron configuration (lowest energy arrangement) of an atom lists orbitals occupied by its electrons. Rules:

1. Lowest-energy orbitals fill first: 1s 2s 2p 3s 3p 4s 3d (Aufbau (“build-up”) principle)

2. Electrons act as if they were spinning around an axis. Electron spin can have only two orientations, up and down . Only two electrons can occupy an orbital, and they must be of opposite spin (Pauli exclusion principle) to have unique wave equations

3. If two or more empty orbitals of equal energy are available, electrons occupy each with spins parallel until all orbitals have one electron (Hund's rule).

31

s

s

ps

pd

sp

d

f

n = 4

n = 3

n = 2

n = 1

The Aufbau The Aufbau (“build-up”) principleprinciple Electrons fill from the

low high.fill n = 1 before n = 2 , fill s before p ...

Electrons don’t share same orbital unless they need to. (i.e. no pairing until each orbital of the set has an e-)

Hund’s RuleHund’s Rule

Each subshell contains orbitals which can hold a max of 2 e-s

e’s in same orbital must be of opposite spins: 1 & 1 .

Pauli Exclusion principlePauli Exclusion principle

1.3 Atomic Structure: Electron 1.3 Atomic Structure: Electron ConfigurationsConfigurations

5d

5s

5p

4d

4f

4s

4p

3d

3s

3p

2s

2p

1s

Major trends in electron fillingMajor trends in electron fillingExceptions:Exceptions:

◦Fill 4s before 3dFill 4s before 3d◦Fill 5s before 4 dFill 5s before 4 d◦Fill 5p before 4fFill 5p before 4f

This is why transition metals are assigned as B group elements.

1s __2s __

2p __ __ __3s __

3p __ __ __4s __ 3d __ __ __ __ __

5s __4p __ __ __

4d __ __ __ __ __ 5p __ __ __

6s __5d __ __ __ __ __

4f __ __ __ __ __ __ __

7733LiLi

1s22s1

Electron ConfigurationElectron Configuration

x y z

x y z

1s __2s __

2p __ __ __3s __

3p __ __ __4s __ 3d __ __ __ __ __

5s __4p __ __ __

4d __ __ __ __ __ 5p __ __ __

6s __5d __ __ __ __ __

4f __ __ __ __ __ __ __

1s22s22p4

1616 88 OO


x y z

1s __2s __

2p __ __ __3s __

3p __ __ __4s __ 3d __ __ __ __ __

5s __4p __ __ __

4d __ __ __ __ __ 5p __ __ __

6s __5d __ __ __ __ __

4f __ __ __ __ __ __ __

1s22s22p63s23p64s23d10

3030ZnZn

[Ar] 4s23d10

[Ar] 3d104s2


x y z

x y z

Classification by sublevelsClassification by sublevelsH

Li

Na

Cs

Rb

K

TlHgAuLsBa

Fr

PtIrOsReWTa

He

RnAtPoBiPb

Be

Mg

Sr

Ca

CdAgY PdRhRuTcMoNb

AcRa

ZnCu

Hf

Zr

TiSc NiCoFeMnCrV

In XeITeSbSn

Ga KrBrSeAsGe

Al ArClSPSi

B NeFONC

Gd

Cm

Tb

Bk

Sm

Pu

Eu

Am

Nd

U

Pm

Np

Ce

Th

Pr

Pa

Yb

No

Lu

Lr

Er

Fm

Tm

Md

Dy

Cf

Ho

Es f

s

d

p

3 - 25

Using the periodic tableUsing the periodic tableto find sublevels to find sublevels

Tl RnAtPoBiPb

In XeITeSbSn

Ga KrBrSeAsGe

Al ArClSPSi

B NeFONC

Gd

Cm

Tb

Bk

Sm

Pu

Eu

Am

Nd

U

Pm

Np

Ce

Th

Pr

Pa

Yb

No

Lu

Lr

Er

Fm

Tm

Md

Dy

Cf

Ho

Es

s

2

3

4

5

H

Li

Na

Cs

Rb

K

Ba

Fr

He

Be

Mg

Sr

Ca

Ra

6

7

1

2

3

4

5

HgAuHfLs PtIrOsReWTa

CdAgZrY PdRhRuTcMoNb

Ac

ZnCuTiSc NiCoFeMnCrV3

4

5

6

d

6

p

f45

Learning Check:Learning Check:

39

Which of the following represents the ground-state electronic configuration for carbon (atomic number 6)?

1. 1s22s22px22py

02pz0

2. 1s22s22px12py

12pz0

3. 1s22s12px12py

1 2pz

1

4. 1s12s22px12py

1 2pz

1

5. 1s22s22px02py

02pz2

Solution:Solution:

40

Which of the following represents the ground-state electronic configuration for carbon (atomic number 6)?

1. 1s22s22px22py

02pz0

2. 1s22s22px12py

12pz0

3. 1s22s12px12py

1 2pz

1

4. 1s12s22px12py

1 2pz

1

5. 1s22s22px02py

02pz2

1111HH

7733LiLi

4422HeHe

9944BeBe 2020

1010NeNe

23231111NaNa

24241212 MgMg

40401818 ArAr

Octet RuleOctet Rule

1s2, 2s1 1s2, 2s2

1s1 1s2

1s2, 2s2 2p6

1s2, 2s2 2p6, 3s1

1s2, 2s2 2p6, 3s2[Ne] 3s1

1s2, 2s2 2p6, 3s2 3p6

1111HH

7733LiLi

23231111NaNa

Lewis StructuresLewis Structures

Show only Valence

Electrons

H

Li

Na

K

H

Li

Na

K

He

Be B C O F NeN

Mg

Ca

Al

Ga

Si

Ge

P

As

S

Se

Cl

Br

Ar

Kr

1

2 3 4 5 6 7

8

Metals give e-s to nonmetals

Nonmetals Share e-s

with other nonmetals

Common ionsCommon ions

H

Li

Na

Cs

Rb

K

TlBa

Fr

He

RnAtPoBiPb

Be

Mg

Sr

Ca

Ra

In XeITeSbSn

Ga KrBrSeAsGe

Al ArClSPSi

B NeFONC

HgAuHfLs PtIrOsReWTa

CdAgZrY PdRhRuTcMoNb

Ac

ZnCuTiSc NiCoFeMnCrV

Gd

Cm

Tb

Bk

Sm

Pu

Eu

Am

Nd

U

Pm

Np

Ce

Th

Pr

Pa

Yb

No

Lu

Lr

Er

Fm

Tm

Md

Dy

Cf

Ho

Es

1+1+

2+2+ 3+3+

4+4+

4-4- 3-3- 2-2- 1-1-

Transition ElementsTransition ElementsVariableVariable

Representative ElementsRepresentative Elements

Formation of NaClFormation of NaCl

Na + Cl Na+ + Cl

+ and - ions attract to form an ionic bond.

_

e- moves from Metal Nonmetal

Metal Cation

Nonmetal Anion

Stable octetsStable octets

Ionic compoundsIonic compounds•Not individual molecules•Form crystal arrays•Ions touch many others •Formula represents the average ion

ratioNaNaClCl

sodiumsodium chloridechlorideNa

NaNa

Cl

Cl Cl

H

Li

Na

K

He

Be B C O F NeN

Mg

Ca

Al

Ga

Si

Ge

P

As

S

Se

Cl

Br

Ar

Kr

1

2 3 4 5 6 7

8

Metals give e-s to nonmetals

Nonmetals Share e-s

with other nonmetals

Covalent BondsCovalent BondsH H+ H H

Cl

O

+ Cl Cl

O +

+N N N N

OO

Cl

Covalent BondsCovalent Bonds

H H

Cl Cl

N N

OO

H-H HH22 Cl-Cl ClCl22

O=O OO22

N N NN22

O C

OC

Covalent BondsCovalent Bonds

O=C=O

C O

O

COCarbon Carbon monmonoxideoxide

Carbon Carbon didioxideoxide CO2

May modify rules to improve sound. ieie - monmonoxide not monomonooxide.

Naming covalent compoundsNaming covalent compoundsCOCO2

N2O5

SiO2

ICl3

P2O5

CCl4May modify rules to improve the sound. ExampleExample - use monoxide not monooxide.

carbon tetrachloridediphophorous pentoxide

iodine trichloridesilicon dioxide

carbon monoxidecarbon dioxide

dinitrogen pentoxide

Review:Review:

CO O

ShapeShape

O=C=O

Linear Shape (180Linear Shape (180oo))

COCO22

F

F B

ShapeShape

(120(120oo))Trigonal PlanarTrigonal Planar

BFBF33

F FB

F

F

1.4 Development of Chemical 1.4 Development of Chemical Bonding TheoryBonding TheoryKekulé and Couper independently observed that

carbon always has four bonds

van't Hoff and Le Bel proposed that the four bonds of carbon have specific spatial directions◦ Atoms surround carbon as corners of a

tetrahedron

60

CH H

O

ShapeShape

O=C=Oe-’s in 2 directions = 180o

LinearLinear

e-’s in 3 directions = 120o

Trigonal planarTrigonal planar

HN

HH

ShapeShape

NH HH

e-’s in 4 directions = 109.5o

PyramidalPyramidal

NH H H

(109.5(109.5oo))Tetrahedral Configuration of ElectronsTetrahedral Configuration of ElectronsTrigonal Pyramid Trigonal Pyramid Configuration of AtomsConfiguration of Atoms

Tetrahedral electron-pair Tetrahedral electron-pair GeometriesGeometries

TetrahedralTetrahedral

PyramidalPyramidalBentBent

71

Non-bonding electronsNon-bonding electronsValence electrons not used in bonding are called

nonbonding electrons, or lone-pair electrons◦ Nitrogen atom in ammonia (NH3)

Shares six valence electrons in three covalent bonds and remaining two valence electrons are nonbonding lone pair

72

Learning CheckLearning CheckHow many hydrogen atoms does phosphorus

bond to in forming phosphine, PH?

73

Hint: Draw the electron dot structure and then use Hydrogen to provided the needed bonded electrons

SolutionSolutionHow many hydrogen atoms does phosphorus

bond to in forming phosphine, PH?

74

Hint: Draw the electron dot structure and then use Hydrogen to provided the needed bonded electrons

3PH

HH H

HPH

Learning CheckLearning CheckHow many hydrogen atoms does Carbon

need in forming chloroform, CH?Cl

75

ClH C

SolutionSolutionHow many hydrogen atoms does Carbon

need in forming chloroform, CH?Cl

HC

H

ClH

76

3

CH

HClH

ClH C

HHCH

Cl

1.5 The Nature of Chemical Bonds: 1.5 The Nature of Chemical Bonds: Valence Bond TheoryValence Bond Theory

Covalent bond forms when two atoms approach each other closely so that a singly occupied orbital on one atom overlaps a singly occupied orbital on the other atom

Two models to describe covalent bonding.

Valence bond theory, Molecular orbital theory

Valence Bond Theory: Electrons are paired in the overlapping orbitals and are attracted to nuclei of both atoms

◦ H–H bond results from the overlap of two singly occupied hydrogen 1s orbitals◦ H-H bond is cylindrically symmetrical,

sigma () bond

77

Bond EnergyBond EnergyReaction 2 H· H2 releases 436 kJ/molProduct has 436 kJ/mol less energy than two atoms:

H–H has bond strength of 436 kJ/mol. (1 kJ = 0.2390 kcal; 1 kcal = 4.184 kJ)

78

Bond LengthBond LengthDistance

between nuclei that leads to maximum stability

If too close, they repel because both are positively charged

If too far apart, bonding is weak

79

1.6 1.6 spsp3 3 Orbitals and the Structure of Orbitals and the Structure of MethaneMethane

Carbon has 4 valence electrons (2s2 2p2) In CH4, all C–H bonds are identical (tetrahedral) sp3 hybrid orbitals: s orbital and three p orbitals

combine to form four equivalent, unsymmetrical, tetrahedral orbitals (sppp = sp3), Pauling (1931)

80

The Structure of MethaneThe Structure of Methanesp3 orbitals on C overlap with 1s orbitals on 4

H atoms to form four identical C-H bondsEach C–H bond has a strength of 436 (438)

kJ/mol and length of 109 pmBond angle: each H–C–H is 109.5°, the

tetrahedral angle.

81

1.7 1.7 spsp3 3 Orbitals and the Structure of Orbitals and the Structure of EthaneEthane

Two C’s bond to each other by overlap of an sp3 orbital from each

Three sp3 orbitals on each C overlap with H 1s orbitals to form six C–H bonds

C–H bond strength in ethane 423 kJ/molC–C bond is 154 pm long and strength is 376

kJ/molAll bond angles of ethane are tetrahedral

82

1.8 1.8 spsp2 2 Orbitals and the Orbitals and the Structure of EthyleneStructure of Ethylene

sp2 hybrid orbitals: 2s orbital combines with two 2p orbitals, giving 3 orbitals (spp = sp2). This results in a double bond.

sp2 orbitals are in a plane with120° angles Remaining p orbital is perpendicular to the

plane

83

Bonds From spBonds From sp22 Hybrid Hybrid OrbitalsOrbitals

Two sp2-hybridized orbitals overlap to form a bondp orbitals overlap side-to-side to formation a pi () bondsp2–sp2 bond and 2p–2p bond result in sharing four

electrons and formation of C-C double bondElectrons in the bond are centered between nucleiElectrons in the bond occupy regions are on either side

of a line between nuclei

84

Structure of EthyleneStructure of Ethylene H atoms form bonds with four sp2 orbitals H–C–H and H–C–C bond angles of about 120°

85

C–C double bond in ethylene shorter and stronger than single bond in ethane

Ethylene C=C bond length 134 pm (C–C 154 pm)

1.9 1.9 spsp Orbitals and the Structure of Orbitals and the Structure of AcetyleneAcetyleneC-C a triple bond sharing six electronsCarbon 2s orbital hybridizes with a single p

orbital giving two sp hybrids◦ two p orbitals remain unchanged

sp orbitals are linear, 180° apart on x-axisTwo p orbitals are perpendicular on the y-axis

and the z-axis

86

Orbitals of AcetyleneOrbitals of AcetyleneTwo sp hybrid orbitals from each C form sp–sp bondpz orbitals from each C form a pz–pz bond by

sideways overlap and py orbitals overlap similarly

87

Bonding in AcetyleneBonding in AcetyleneSharing of six electrons forms C C

Two sp orbitals form bonds with hydrogens

88

89

1.10 Hybridization of Nitrogen 1.10 Hybridization of Nitrogen and Oxygenand Oxygen

Elements other than C can have hybridized orbitals

H–N–H bond angle in ammonia (NH3) 107.3°C-N-H bond angle is 110.3 °N’s orbitals (sppp) hybridize to form four sp3

orbitalsOne sp3 orbital is occupied by two nonbonding

electrons, and three sp3 orbitals have one electron each, forming bonds to H and CH3.

90

1.11 Molecular Orbital 1.11 Molecular Orbital TheoryTheory

A molecular orbital (MO): where electrons are most likely to be found (specific energy and general shape) in a molecule

Additive combination (bonding) MO is lower in energy

Subtractive combination (antibonding) MO is higher energy

91

Molecular Orbitals in Molecular Orbitals in EthyleneEthylene

The bonding MO is from combining p orbital lobes with the same algebraic sign

The antibonding MO is from combining lobes with opposite signs

Only bonding MO is occupied

92

1.12 Drawing Structures1.12 Drawing StructuresDrawing every bond in organic

molecule can become tedious.Several shorthand methods have

been developed to write structures.

Condensed structures don’t have C-H or C-C single bonds shown. They are understood.

e.g. 93

3 General Rules:1) Carbon atoms aren’t usually shown. Instead a

carbon atom is assumed to be at each intersection of two lines (bonds) and at the end of each line.

2) Hydrogen atoms bonded to carbon aren’t shown.

3) Atoms other than carbon and hydrogen are shown (See table 1.3).

94

SummarySummary Organic chemistry – chemistry of carbon compounds Atom: positively charged nucleus surrounded by

negatively charged electrons Electronic structure of an atom described by wave

equation◦ Electrons occupy orbitals around the nucleus.◦ Different orbitals have different energy levels and

different shapes s orbitals are spherical, p orbitals are dumbbell-

shaped Covalent bonds - electron pair is shared between

atoms Valence bond theory - electron sharing occurs by

overlap of two atomic orbitals Molecular orbital (MO) theory, - bonds result from

combination of atomic orbitals to give molecular orbitals, which belong to the entire molecule

95

Summary (cont’d)Summary (cont’d) Sigma () bonds - Circular cross-section and are

formed by head-on interaction Pi () bonds – “dumbbell” shape from sideways

interaction of p orbitals Carbon uses hybrid orbitals to form bonds in organic

molecules.◦ In single bonds with tetrahedral geometry, carbon has

four sp3 hybrid orbitals◦ In double bonds with planar geometry, carbon uses

three equivalent sp2 hybrid orbitals and one unhybridized p orbital

◦ Carbon uses two equivalent sp hybrid orbitals to form a triple bond with linear geometry, with two unhybridized p orbitals

Atoms such as nitrogen and oxygen hybridize to form strong, oriented bonds◦ The nitrogen atom in ammonia and the oxygen atom

in water are sp3-hybridized

96


97

Based on the octet rule, which line-bond Based on the octet rule, which line-bond structures is/are correct?structures is/are correct?

CH

HH

C C HH

CH

HH

C C H CH

HH

C C HH

CH

HH

C C HH H

A B C D

1. A and B2. A and C3. B and D4. Only B5. Only C

Solution:Solution:

98

Based on the octet rule, which line-bond Based on the octet rule, which line-bond structures is/are correct?structures is/are correct?

CH

HH

C C HH

CH

HH

C C H CH

HH

C C HH

CH

HH

C C HH H

A B C D

1. A and B2. A and C3. B and D4. Only B5. Only C

Which of these statements concerning Which of these statements concerning pp--orbitals is orbitals is falsefalse??

1. They consist of two equivalent lobes.2. They are absent from the first shell of

atomic orbitals.3. They can form π bonds.4. They only participate in bonding on

carbon atoms.5. They can hold a maximum of two

electrons.99


Which of these statements concerning Which of these statements concerning pp--orbitals is orbitals is falsefalse??

1. They consist of two equivalent lobes.2. They are absent from the first shell of

atomic orbitals.3. They can form π bonds.4. They only participate in bonding on

carbon atoms.5. They can hold a maximum of two

electrons.100

Solution:Solution:

What is the hybridization of the oxygen-What is the hybridization of the oxygen-bonded carbon atom in the following bonded carbon atom in the following molecule? molecule?

1. s2. p3. sp4. sp2

5. sp3

101

N CH3C

O


What is the hybridization of the oxygen-What is the hybridization of the oxygen-bonded carbon atom in the following bonded carbon atom in the following molecule? molecule?

1. s2. p3. sp4. sp2

5. sp3

102

N CH3C

O

Solution:Solution:

What is the hybridization of nitrogen What is the hybridization of nitrogen atom in trimethylamine :N(CHatom in trimethylamine :N(CH33))33??

1. sp2. sp2

3. sp3

4. dsp2

5. unhybridized

103


What is the hybridization of nitrogen What is the hybridization of nitrogen atom in trimethylamine :N(CHatom in trimethylamine :N(CH33))33??

1. sp2. sp2

3. sp3

4. dsp2

5. unhybridized

104

Solution:Solution:

What type of orbital What type of orbital is notis not used in used in constructing the molecule shown below?constructing the molecule shown below?

1. s2. p3. sp4. sp2

5. sp3

105

O

O


What type of orbital What type of orbital is notis not used in used in constructing the molecule shown below?constructing the molecule shown below?

1. s2. p3. sp4. sp2

5. sp3

106

O

O

Solution:Solution:

What is the molecular formula of the What is the molecular formula of the molecule shown below? molecule shown below?

1. C8H12O2. C8H11O3. C8H7O4. C7H7O5. C7H10O

107

O


What is the molecular formula of the What is the molecular formula of the molecule shown below? molecule shown below?

1. C8H12O2. C8H11O3. C8H7O4. C7H7O5. C7H10O

108

O

Solution:Solution:

Electrons cannot occupy an antibonding Electrons cannot occupy an antibonding molecular orbital.molecular orbital.

1. True2. False

109


Electrons cannot occupy an antibonding Electrons cannot occupy an antibonding molecular orbital.molecular orbital.

1. True2. False

110

Solution:Solution:

How many hydrogen atoms are present in the How many hydrogen atoms are present in the naturally-occurring terpene α-terpinene shown naturally-occurring terpene α-terpinene shown below?below?

1. 142. 153. 164. 175. 18

111


How many hydrogen atoms are present in the How many hydrogen atoms are present in the naturally-occurring terpene α-terpinene shown naturally-occurring terpene α-terpinene shown below?below?

1. 142. 153. 164. 175. 18

112

Solution:Solution:

Select the best condensed structural Select the best condensed structural formula for the following molecule:formula for the following molecule:

1. (CH3)2CHCH2COHOHCOH2. CH3CH3CHCH2C(OH)2CHO3. (CH3)2CHCH2C(OH)2CHO4. (CH3)2CHCH2C(OH)2COH5. CH3CHCH3CH2C(OH)2CHO

113

HHO OH

O


Select the best condensed structural Select the best condensed structural formula for the following molecule:formula for the following molecule:

1. (CH3)2CHCH2COHOHCOH2. CH3CH3CHCH2C(OH)2CHO3. (CH3)2CHCH2C(OH)2CHO4. (CH3)2CHCH2C(OH)2COH5. CH3CHCH3CH2C(OH)2CHO

114

HHO OH

O

Solution:Solution:

What is the correct order of carbon-What is the correct order of carbon-carbon bond lengths in ethane, ethylene carbon bond lengths in ethane, ethylene and acetylene?and acetylene?1. ethane < ethylene < acetylene2. ethane < acetylene < ethylene3. ethylene < ethane < acetylene4. ethylene < acetylene < ethane5. acetylene < ethane < ethylene6. acetylene < ethylene < ethane

115


What is the correct order of carbon-What is the correct order of carbon-carbon bond lengths in ethane, ethylene carbon bond lengths in ethane, ethylene and acetylene?and acetylene?1. ethane < ethylene < acetylene2. ethane < acetylene < ethylene3. ethylene < ethane < acetylene4. ethylene < acetylene < ethane5. acetylene < ethane < ethylene6. acetylene < ethylene < ethane

116

Solution:Solution:

What kind of orbital and with how many What kind of orbital and with how many nodal planes is shown in the picture nodal planes is shown in the picture below?below?

1. σ antibonding, two nodal planes2. σ antibonding, one nodal plane3. π bonding, one nodal plane4. π antibonding, two nodal planes5. π antibonding, one nodal plane

117


What kind of orbital and with how many What kind of orbital and with how many nodal planes is shown in the picture nodal planes is shown in the picture below?below?

1. σ antibonding, two nodal planes2. σ antibonding, one nodal plane3. π bonding, one nodal plane4. π antibonding, two nodal planes5. π antibonding, one nodal plane

118

Solution:Solution:

What is the best description of bond What is the best description of bond length?length?

1. a distance between nuclei that yields the best orbital overlap

2. a distance between nuclei that yields the smallest nuclear-nuclear repulsion

3. a distance between nuclei that yields the smallest electron-electron repulsion

4. a distance between nuclei that yields the largest electron-nuclei attraction

5. a distance between nuclei that is a compromise of all electrostatic interactions

119


What is the best description of bond What is the best description of bond length?length?

1. a distance between nuclei that yields the best orbital overlap

2. a distance between nuclei that yields the smallest nuclear-nuclear repulsion

3. a distance between nuclei that yields the smallest electron-electron repulsion

4. a distance between nuclei that yields the largest electron-nuclei attraction

5. a distance between nuclei that is a compromise of all electrostatic interactions

120

Solution:Solution:

What is the O-C-O bond angle in What is the O-C-O bond angle in potassium carbonate, Kpotassium carbonate, K22COCO33??

1. 60°2. 90°3. 109.5°4. 120°5. 180°

121


What is the O-C-O bond angle in What is the O-C-O bond angle in potassium carbonate, Kpotassium carbonate, K22COCO33??

1. 60°2. 90°3. 109.5°4. 120°5. 180°

122

Solution:Solution:

What is the relative orientation of What is the relative orientation of two two ππ orbitals in acetylene? orbitals in acetylene?

1. 60°2. 90°3. 109.5°4. 120°5. 180°

123


What is the relative orientation of What is the relative orientation of two two ππ orbitals in acetylene? orbitals in acetylene?

1. 60°2. 90°3. 109.5°4. 120°5. 180°

124

Solution:Solution:

In relation to In relation to σσ bonds, which bonds, which statement about statement about ππ bonds is correct? bonds is correct?

1. π bonds are weaker and π electrons have higher energy

2. π bonds are stronger and π electrons have higher energy

3. π bonds are weaker and π electrons have lower energy

4. π bonds are stronger and π electrons have lower energy

5. π bonds and σ bonds have equal strengths, and their electrons have the same energies

125


In relation to In relation to σσ bonds, which bonds, which statement about statement about ππ bonds is correct? bonds is correct?

1. π bonds are weaker and π electrons have higher energy

2. π bonds are stronger and π electrons have higher energy

3. π bonds are weaker and π electrons have lower energy

4. π bonds are stronger and π electrons have lower energy

5. π bonds and σ bonds have equal strengths, and their electrons have the same energies

126

Solution:Solution:

Which of the orbitals shown below can be Which of the orbitals shown below can be occupied in a hydrogen atom?occupied in a hydrogen atom?

1. A2. B3. C4. D5. Any one of these

127

A B C D


Which of the orbitals shown below can be Which of the orbitals shown below can be occupied in a hydrogen atom?occupied in a hydrogen atom?

1. A2. B3. C4. D5. Any one of these

128

A B C D

Solution:Solution:

Which statement about the antibonding Which statement about the antibonding orbital in Horbital in H22 is is falsefalse??

1. It is higher in energy than the corresponding bonding orbital

2. It is a molecular orbital3. It has a nodal plane (a node for

short)4. It can hold up to two electrons5. The two lobes have different

charges129


Which statement about the antibonding Which statement about the antibonding orbital in Horbital in H22 is is falsefalse??

1. It is higher in energy than the corresponding bonding orbital

2. It is a molecular orbital3. It has a nodal plane (a node for

short)4. It can hold up to two electrons5. The two lobes have different

charges130

Solution:Solution:

What is the hybridization of nitrogen What is the hybridization of nitrogen in :NCCHin :NCCH33??

1. sp2. sp2

3. sp3

4. sp3d5. nitrogen is not

hybridized

131


What is the hybridization of nitrogen What is the hybridization of nitrogen in :NCCHin :NCCH33??

1. sp2. sp2

3. sp3

4. sp3d5. nitrogen is not

hybridized

132

Solution:Solution:

Hotel ModelHotel Model

s

s

ps

pd

sp

df

n = 4 (4th floor)

n = 3 (3rd floor)

n = 2 (2nd floor)

n = 1 (1st floor)

Each shell (floor of the Hotel) Has subshells (s,p,d,f)

2 e-

8 e-

18 e-

32 e-

Documents

1 CH241 Structure & Bonding