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chem 24 > exam 2 > Flashcards

exam 2 Flashcards

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1
Q

The strongest acid will have

A

the most stable conjugate base

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2
Q

what makes a base more stable

A

Atom, resonance, induction, orbital

delocalization of a negative charge will be the most stable

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3
Q

what is the atom effect on a bases stability?

A

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

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4
Q

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

A

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

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5
Q

what is the inductive effect?

A

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

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6
Q

what is the orbital effect?

A

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)

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7
Q

how much s character is in sp

A

50%, 50%

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8
Q

how much s character is in sp2

A

33% s, 66% p character

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9
Q

how much s character is in sp3

A

25% s, 75% p character

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10
Q

what are the different types of hydrocarbons

A

saturated and unsaturated

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11
Q

what are saturated hydrocarbons

A

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

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12
Q

what are unsaturated hydrocarbons

A

they have less than the maximum number of carbons

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13
Q

whats the formula for a saturated hydrocarbon

A

CnH2n+2

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14
Q

whats the formula for unsaturated hydrocarbons

A

CnH2n

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15
Q

2hats the formula for unsaturated alkynes

A

CnH2n-2

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16
Q

what is one degree of unsaturation

A

1 pi bond or a ring

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17
Q

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

A

you lose 2 hydrogens each time

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18
Q

what are conformations

A

rotation about single bonds results in different conformations

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19
Q

which conformation is the most stable?

A

the conformation with the hydrogens more spread out

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20
Q

what is the steric effect?

A

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.

21
Q

what are the different types of conformations?

A

fully eclipsed, gauche, eclipsed, anti

22
Q

what is a fully eclipsed conformation

A

when the two methyl groups fully eclipse eachother

23
Q

what is a gauche conformation

A

when the methyl groups are staggered but next to eachother

24
Q

what is an eclipsed conformation

A

when the methyl groups eclipse the hydrogen atoms

25
Q

what is an anti conformation

A

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

26
Q

which conformation is the highest in energy

A

the fully eclipsed

27
Q

how do you tell which conformation is more stable?

A

the one where the electrons are spread out the furthest apart

28
Q

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

A

4 kj/mol for each eclipse

29
Q

what conformation does equilibrium favor?

A

The one lowest in energy (typically staggered)

30
Q

what is a conformation?

A

the result of rotations about a single bond

31
Q

What is a torsional strain

A

it is the strain that results from eclipsing

32
Q

what is steric strain

A

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

33
Q

Is cyclopropane stable, why or why not

A

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

34
Q

why do we look down specific carbon-carbon bonds

A

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

35
Q

draw the envelope conformation of cyclopentane

A
36
Q

What is special about cyclohexane?

A

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)

37
Q

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

A

it contains steric strains from the two hydrogens being close together

it also have torsional strain from the eclipsing of hydrogens

38
Q

what are axial hydrogens

A

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

39
Q

what are equatorial hydrogens

A

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

40
Q

how do you name alkenes

A

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

41
Q

how do you name an alkene with a alcohol?

A

the alcohol takes priority and should have the lowest number

42
Q

what do we need to consider when naming alkenes?

A

cis and trans stereochemistry

43
Q

when is something cis for alkenes?

A

when the identical substitutuents are on the same side

44
Q

when is something trans for alkenes

A

when the subst. are on opposite sides

45
Q

does ethane have steric strain?

A

no, just torsional strain when eclipsed

46
Q

when is a cycloalkane cis

A

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

47
Q

when is a cycloalkane trans

A

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

48
Q
A
49
Q

how many degrees of unsaturation does an alkyne have

A

2

chem 24 (22 decks)

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