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OCHEM > Chapter 6 > Flashcards

Chapter 6 Flashcards

1
Q

The chemistry of vinyl and aryl halides is different from that of alkyl halides because of their _______ and _______

A

bonding and hybridization

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2
Q

halogens are more _______ than carbon, making the C-X bond _______

A

electronegative
polar

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3
Q

For common (“trivial”) name as alkyl halide
1) name the _______ group
2) name the _______

A

alkyl
halide

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4
Q

_______ dihalide: two halogen atoms are bonded to the same carbon

A

geminal

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5
Q

______________ dihalide: two halogen atoms are bonded to adjacent carbons

A

vicinal

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6
Q

the larger the surface area of an alkyl halide, the _______ the boiling point
- Larger _______ take priority

A

higher
halogen

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7
Q

alkyl flourides and chlorides are _______ dense than water, so in bilayer it will occupy the _______ layer

A

less
top

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8
Q

alkyl chlorides with 2 or more Cl atoms are _______ dense than water, so in bilayer it will occupy the _______ layer

A

more
bottom

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9
Q

all alkyl bromides and iodides are _______ dense than water

A

more

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10
Q

What are the 2 types of substitution reactions?

A

1) bonds broken and formed at the same time (Sn2)
2) old bond breaks, then new bond forms (Sn1)

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11
Q

bimolecular nucleophilic substitution (_______) have __ molecules in r.d.s

A

Sn2
2

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12
Q

Sn2 reactions are ___-step reactions, where the bond is broken and formed _______

A

1
simultaneously (concerted)

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13
Q

What type of intermediate is present in the SN2 reaction of cyanide with bromoethane?

A

there is no intermediate

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14
Q

What are the 3 options that could result from attack at the chiral electrophilic carbon

A

1) retention
2) inversion
3) racemization

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15
Q

Sn2 reactions occur with 100% _______ of configuration at the electrophilic carbon. This is a _______ reaction

A

inversion
stereospecific

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16
Q

to form a new bond, the _______ must approach the electrophilic C from the side that is _______ of the leaving group. This is called a _______

A

nucleophile
opposite
backside attack

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17
Q

The best leaving groups are
1) _______: strong EN creates a partial positive on carbon
2) stable:
3) polarizable:

A

1) electron-withdrawing
2) should be weak bases (conjugate bases of strong acids)
3) maintain partial bonding with the carbon atom in the TS

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18
Q

What is the most common leaving group that we will see in Sn2 reactions?

A

sulfonate

19
Q

different alkyl halides undergo Sn2 reactions at different rates:
1) place your focus on the carbon attached to the leaving group, this is the _______ C
2) _______ hindrance plays a large role in the rate of Sn2 reactions

A

electrophilic
steric

20
Q

________ stabilizes the transition state which results in the _______ of the rate

A

resonance
increase

21
Q

Sn1 reactions have ___ molecule in r.d.s

A

1

22
Q

The rate of Sn1 reactions are completely dependant on the concentration of the _______

A

electrophile

23
Q

SN1 reactions are ___-step reaction where the old bond is broken first and then the new bond is formed

A

2

24
Q

What are the steps to an Sn1 reaction?

A

1) LG leaves
2) nucleophile attacks carbocation
3) solvent attacks new positive charge

25
Q

The rate-limiting step of the Sn1 reaction is ionization to form a carbocation which is an extremely _______ process

A

endothermic

26
Q

Hammonds postulate: the structure of the transition state most resembles the species to which it is closest in _______

A

energy

27
Q

rates of Sn1 reactions depend strongly on _______ stability
- then depends on _______

A

carbocation
leaving group

28
Q

rank 1°, 2°, and 3° and their allylic and benzylics for Sn1 rates

A

3°allylic and benzylic > 3°, 2° allylic and benzylic > 2°, 1° allylic and benzylic > 1°

29
Q

In the Sn1 mechanism, the carbocation formed is _______ and _______

A

planar
achiral

30
Q

Sn1: attack from both faces gives _______ enantiomers of the product

A

50% retention
50% inversion
racemic mixture
- little more inversion

31
Q

Trends in nucleophiles (Sn2):
1) when comparing charged vs neutral, _______ is stronger
2) nucleophilicity _______ from left to right in the periodic table
3) in the same group (column), nucleophilicity _______ as you move down
4) bulky groups _______ nucleophilicity due to their steric hindrance

A

1) charged
2) decreases
3) increases
4) decrease

32
Q

more EN atoms have more tight held nonbonding electrons that are _______ reactive toward forming new bonds

A

less

33
Q

Solvent: a liquid that can dissolve the _______. It interacts with reactants, products, and intermediates during the reaction process

A

reactants

34
Q

What are the 2 main types of solvents?

A

1) polar protic (p/p)
- SN1
2) polar aprotic
- SN2

35
Q

_______ solvents have acidic hydrogens (O-H and N-H) that can solvate the nucleophile, reducing their nucleophilicity

A

polar protic (p/p)

36
Q

_______ solvents do not have acidic protons and cannot hydrogen bond

A

polar aprotic

37
Q

What is one example of a polar protic solvent?

A

EtOH or H2O

38
Q

What is one example of a polar aprotic solvent?

A

THF or diethyl ether

39
Q

Carbocations (C+) frequently undergo structural changes called rearrangements to form more stable ions when possible. What are the 2 different rearrangements?

A

1) hydride shift
2) alkyl shift

40
Q

In Hydride shift, you can _______ make the C+ worse or same, you have to make it _______

A

never
better

41
Q

In Alkyl shift, an ________ group can rearrange to make the carbocation more stable

A

alkyl

42
Q

What are the steps to ring expansion?

A

1) check carbocation to see if you can relieve ring strain
2) then look at C+ stability
- Ring strain trumps C+ stability

43
Q

_______: both nucleophile and electrophile within the same molecule

A

intramolecular

44
Q

When you have an intramolecular molecule, what are you allowed to do to the molecule?

A

cyclizations or ring formation

OCHEM (12 decks)

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