exam 2

Question 1

The strongest acid will have

Answer 1

the most stable conjugate base

Question 2

what makes a base more stable

Answer 2

Atom, resonance, induction, orbital

delocalization of a negative charge will be the most stable

Question 3

what is the atom effect on a bases stability?

Answer 3

when moving across a row, the most electronegative atom will be the most stable

when moving down a column, the larger atom will be the most stable

in general, larger atoms trump more electronegative atoms

Question 4

what is the resonance effect on a base’s stability?

Answer 4

resonance allows for delocalization of the negative charge which is lower in energy

the conj. base with the most resonance structures will be the most stable

Question 5

what is the inductive effect?

Answer 5

the electronegativity of an atom will induce a “through bond effect” that decreases with distance

the closer the electronegative is to the negative charge, the stronger the pull is

Question 6

what is the orbital effect?

Answer 6

when the lone pair is residing within an orbital with more s character (sp>sp2>sp3) it will be more stable since s orbitals are closer to the nucleus (which is positively charged)

Question 7

how much s character is in sp

Answer 7

50%, 50%

Question 8

how much s character is in sp2

Answer 8

33% s, 66% p character

Question 9

how much s character is in sp3

Answer 9

25% s, 75% p character

Question 10

what are the different types of hydrocarbons

Answer 10

saturated and unsaturated

Question 11

what are saturated hydrocarbons

Answer 11

saturated hydrocarbons have the maximum number of carbons ( single bonds)

Question 12

what are unsaturated hydrocarbons

Answer 12

they have less than the maximum number of carbons

Question 13

whats the formula for a saturated hydrocarbon

Answer 13

CnH2n+2

Question 14

whats the formula for unsaturated hydrocarbons

Answer 14

CnH2n

Question 15

2hats the formula for unsaturated alkynes

Answer 15

CnH2n-2

Question 16

what is one degree of unsaturation

Answer 16

1 pi bond or a ring

Question 17

if you add more bonds, what happens to the hydrogens?

Answer 17

you lose 2 hydrogens each time

Question 18

what are conformations

Answer 18

rotation about single bonds results in different conformations

Question 19

which conformation is the most stable?

Answer 19

the conformation with the hydrogens more spread out

Question 20

what is the steric effect?

Answer 20

Steric effects arise from the spatial arrangement of atoms. When atoms come close together there is generally a rise in the energy of the molecule.

Question 21

what are the different types of conformations?

Answer 21

fully eclipsed, gauche, eclipsed, anti

Question 22

what is a fully eclipsed conformation

Answer 22

when the two methyl groups fully eclipse eachother

Question 23

what is a gauche conformation

Answer 23

when the methyl groups are staggered but next to eachother

Question 24

what is an eclipsed conformation

Answer 24

when the methyl groups eclipse the hydrogen atoms

Question 25

what is an anti conformation

Answer 25

when the methyl groups are staggered as far away from eachother as possible

Question 26

which conformation is the highest in energy

Answer 26

the fully eclipsed

Question 27

how do you tell which conformation is more stable?

Answer 27

the one where the electrons are spread out the furthest apart

Question 28

what is the torsional strain energy associated with a C-H eclipsed bond in ethane?

Answer 28

4 kj/mol for each eclipse

Question 29

what conformation does equilibrium favor?

Answer 29

The one lowest in energy (typically staggered)

Question 30

what is a conformation?

Answer 30

the result of rotations about a single bond

Question 31

What is a torsional strain

Answer 31

it is the strain that results from eclipsing

Question 32

what is steric strain

Answer 32

it is the strain that results from bulky groups interacting too closely in a conformation

Question 33

Is cyclopropane stable, why or why not

Answer 33

it is not very stable because it has a very high ring strain and an angle of 60° rather than 109.5° it also has torsional strain from eclipse C-H bonds all around

Question 34

why do we look down specific carbon-carbon bonds

Answer 34

if we look top down it looks planar but if we look from a newman projection we can see the various strains

Question 35

draw the envelope conformation of cyclopentane

Question 36

What is special about cyclohexane?

Answer 36

it is the lowest in energy, i t is very stable, there is no angle strain (all carbons have a 109.5°) there is no torsional strain (all hydrogens are staggered)

Question 37

why is the boat conformation higher in energy than the chair conformation?

Answer 37

it contains steric strains from the two hydrogens being close together it also have torsional strain from the eclipsing of hydrogens

Question 38

what are axial hydrogens

Answer 38

hydrogens in the chair conformation that are pointing straight up and down

Question 39

what are equatorial hydrogens

Answer 39

hydrogens in the chair conformations that are parallel with various sides of the chair conformation (alternating up and down)

Question 40

how do you name alkenes

Answer 40

write it with the lowest number in front of the parent chain

Question 41

how do you name an alkene with a alcohol?

Answer 41

the alcohol takes priority and should have the lowest number

Question 42

what do we need to consider when naming alkenes?

Answer 42

cis and trans stereochemistry

Question 43

when is something cis for alkenes?

Answer 43

when the identical substitutuents are on the same side

Question 44

when is something trans for alkenes

Answer 44

when the subst. are on opposite sides

Question 45

does ethane have steric strain?

Answer 45

no, just torsional strain when eclipsed

Question 46

when is a cycloalkane cis

Answer 46

when they point off the same face of the ring (both either dashed or both wedges)

Question 47

when is a cycloalkane trans

Answer 47

when they point off of opposite sides of the ring (one wedge one dash)

Question 49

how many degrees of unsaturation does an alkyne have

Answer 49

2