Chapter 2

Question 1

What is this style of describing a compound?

Answer 1

Lewis Structure

Question 2

What is this style of describing a compound?

Answer 2

Partially Condesnsed Structure

C-H bonds are not all drawn explicitly

Question 3

What is this style of describing a compound?

Answer 3

Condensed Structure

single atoms are not draw and groups of atoms are clustered together (when possible)

Question 4

What is this style of describing a compound?

Answer 4

Molecular Formula

conveys no structural information

Question 5

What is a constitutional isomer?

Answer 5

same molecular formula,

different structure

Question 6

What is this style of describing a compound?

Answer 6

Bond-Line Structures

• each corner is a carbon
• hydrogens are not drawn on carbons
• heteroatoms (not carbon or hydrogen) are drawn
• hydrogens connected to heteroatoms are drawn

Question 7

define functional group

Answer 7

a functional group is a characteristic group of atoms/bonds that have a predictable chemical behavior

(ex: endorphins, codeine, morphine, heroin)

Question 8

describe + formal charge

Answer 8

+ formal charge is having more protons in the nucleus than electrons surround it

(always remembering the 1s shell)

Question 9

describe - formal charge

Answer 9

• formal charge is having more electrons around the atom than protons in the nucleus

(always remembering the 1s shell)

Question 10

describe how to determine formal charge

Answer 10

1. determine appropriate number of valence electrons for the atom (to balance out protons in the nucleus)
2. determine how many electrons are actually around the atom

bond - contributes 1 electron

lone pair - contributes 2 electrons

Question 11

describe molecular orbital theory

Answer 11

in molecular orbital theory, some orbitals normally around an atom no longer exist, but have instead merged to form molecular orbitals for the entire molecule.

these orbitals are filled with the 2 electrons from each pi bond

–> resulting charge around one atom is actually associated with the whole molecule

Question 12

what 3 types of molecular orbitals can form from the 3 p orbitals? (draw & # nodes)

Answer 12

antibonding MO –highest energy –2 vertical nodes

non-bonding MO –middle energy –1 vertical node

–will not form if only 2 p orbitals contribute

bonding MO –lowest energy –no vertical nodes

Question 13

what are resonance structures?

Answer 13

resonance structures are multiple drawings of the same compound that indicate all of its merged (partial) properties

Question 14

what is a resonance hybrid?

Answer 14

a resonance hybrid is the actual, real molecule which is represented by the resonance structures.

it contains partial characteristics of each drawing in the resonance structure

Question 15

what is delocalization of charge?

Answer 15

delocalization of charge is when the charge (+ or -) is spread out over the molecule

Question 16

which is more stable, compounds with localized charge or compounds with delocalized charge?

Answer 16

delocalized charge

Question 17

are molecules with resonance structures more or less stable (than an equivalent compound without resonance structures)?

Answer 17

more –> resonance stabilization

Question 18

what is resonance stabilization?

Answer 18

resonance hybrids are more stable (than a similar, non-resonant compound) because the charge (+ or -) is delocalized

Question 19

what 2 things must you avoid doing while drawing resonance structures?

Answer 19

1. breaking a single bond
2. exceeding an octet for second-row elements

Question 20

what position are these carbon atoms in?

Answer 20

vinylic position

the carbon atoms participating in the double-carbon-bond

Question 21

what position are these carbon atoms in?

Answer 21

allylic positions

the atoms directly connected to the double-bonded carbon atoms

Question 22

what resonance structure pattern applies to this compound?

Answer 22

allylic lone pair

Question 23

what resonance structure pattern applies to this compound?

Answer 23

allylic positive charge (allylic cation)

Question 24

what resonance structure pattern applies to this compound?

Answer 24

lone pair adjacent to a positive charge

Question 25

what resonance structure pattern applies to this compound?

Answer 25

a pi bond between 2 atoms of differing electronegativity

(especially C=O and C=N)

Question 26

what resonance structure pattern applies to this compound?

Answer 26

conjugated pi bonds enclosed in a ring

Question 27

what can help you determine the significance of resonance structures?

Answer 27

1. most significant resonance structures are those in which all atoms have an octet
2. more significant resonance structures have minimal charges (no more than 2 charges)
3. less significant resonance structure are those in which carbon atoms bear opposite charges

Question 28

what is a localized lone pair?

Answer 28

a localized lone pair cannot participate in resonance. it is not allylic to a pi bond, and thus stays attached to 1 atom.

Question 29

an atom with a lone pair and a pi bond – which electrons participate in resonance

Answer 29

either, but not both

(the lone pair and the pi bond on one atom will not both participate in resonance)