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OChem 1 > Quiz 4 > Flashcards

Quiz 4 Flashcards

1
Q

Fischer projections

A

used to draw complex molecules (usually sugars) with multiple chiral centers

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2
Q

are the horizontal lines on a fichser projection dashed or wedged?

A

horizontal lines are wedged/ coming out of page

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3
Q

Are vertical lines on a Fischer projection dashed or wedged?

A

dashed/ going into the page

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4
Q

why does the reaction happen? are products more stable than reactants?

A

thermodynamics

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5
Q

how does the reaction happen? how do temperature and concentration affect the rate of reaction? How fast does the reaction happen?

A

Kinetics

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6
Q

enthalpy (H)

A

the exchange of energy between a system and its surroundings for any process

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7
Q

to calculate heat of reaction its — minus —

A

reactants minus products

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8
Q

True or false?

Most reactions will require the breaking and forming of bonds

A

True, think about all the reaction mechanisms you will learn

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9
Q

Entropy (S)

A

The measure of disorder within a system

using probablity and liklihood

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10
Q

What sign of enthalpy is favorable and nonfavorable

A

posititve enthalpy (endothermic)= non favorbale
negative enthalpy (exothermic)= favorbale

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11
Q

What sign of entropy is favorable and non favorbale?

A

positive entropy = favorable
negative entropy = non favorable

needs to be positive so G can be negative

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12
Q

What sign of G indicates a spontaneous reaction?

A

negative g

positive g is non spon

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13
Q

negative G, where products are lower energy than reactants, spontaneous

A

exergonic

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14
Q

positive g, where products are higher energy than reactions, non spon

A

endergonic

like how endothermic is not favorbale, neither is endergonic

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15
Q

Keq> 1

A

products are favored, reaction proceeds towards products

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16
Q

Keq<1

A

reactants are favored, reaction proceeds towards reactants

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17
Q

Keq = 1

A

rxn is at equilibrium

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18
Q

True or false?

Spontanenous does not mean slow!

A

false, spontaneous does not mean fast!

but ig it also doesnt mean the first thing

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19
Q

Name the four factors that can affect the rate constant

A
  1. Energy of activation
  2. Temperature
  3. Steric/ geometric orientation
  4. presence of a catalyst
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20
Q

True or false?

A catalyst can speed up a reaction by lowering the Ea by changing transition state orientation?

A

false! a catalyst can never lower the energy of activation

21
Q

transition state

A

the peaks of an energy diagram, where bonds are actively being broken and formed, unstable/high energy

22
Q

What can a transition state tell you about the number of mechanistic steps of a reaction?

A

the number of tranisition states on the graph show the number of mechanistic steps

23
Q

Intermediates

A

certain, but short lifespan, appear on the wells of the graph, more stable/lower energy

24
Q

Activation energy

A

the amount of energy it takes to complete a reaction, the more it takes the slower the reaction

25
Q

Hammonds Postulate

A
  • in exergonic reactions, the transition states are closer in energy to the reactants so they will structurally be more similar to the reactants
  • in endergonic reactions, the transition states are closer in energy to the products so they will structurally be more similar to the products
26
Q

Nucleophile

A

electron dense wants to give up electrons
- often negatively charged or w/ a l.p.
- double bonds (electron dense)
- lewis base

27
Q

examples of nucleophiles

A
  1. halides (NOT ALKYL HALIDES)
  2. bases
  3. alcohols
  4. water (weak nucleophile)
28
Q

electrophiles

A

e-deficient, accepts lone pairs
- often a positive charge
- lewis acid

29
Q

examples of electrophiles

A
  1. alkyl halides
  2. carbonyl groups
  3. carbocations
30
Q

Arrows starts at a place of electron — and points to a place of electron —

A

density, deficiency

31
Q

nucleophilic attack

A

nucleophile attacks and attatches to electrophile
- arrow from negative charge to positive charge

32
Q

Loss of a leaving group

A

grp skedaddles off of molecule (often a terminal halogen)
- one atom takes both e-

33
Q

Proton transfer

acid/base

A

two arrows, proton leaves one atom and moves to another

34
Q

carbocation re-arrangement

A

stabilizing a carbocation by moving a methyl or hydride grp to fill empty p orbital w/ electrons

35
Q

True or false?

Nucleophilic attack should be drawn in before a carbocation re-arrangement?

A

False, a carbocation ion will stabilize with re-arragnment before attack if it can

36
Q

True or false?

methyl and hydride shifts can occur with any methyl or hydride grp on a molecule?

A

false, it can only be adjacent methyls or hydrides

37
Q

Steps to determining if a re-arrangement is right

A
  1. Identify all adjacent carbons to the carbocation
  2. Identify all adjacent methyl and hydride groups
  3. draw out methyl and hydride shift to see if either create a more stable carbocation
38
Q

substitution reactions

A

nucleophile replaces alkyl halide on the molecule

nucleophilic attack + loss.of leaving grp

39
Q

elimination reactions

A

reagents act as a base for a proton transfer and formation of pi bond

proton transfer + loss of leaving grp

40
Q

true or false?

Substitution and elimination reactions only occur at Sp3 hybridized carbon atoms.

A

True, sp2 has too high of activation barrier

41
Q

What are two reasons halogens promote substitution and elimination reactions?

A
  1. Halogens draw e-density away by induction creating a e- deficient place for nucleophilic attack
  2. alkyl halides make good leaving groups
42
Q

alpha carbon

A

carbon directly attatched to alkyl halide

43
Q

beta carbon

A

carbon adjacent to alkyl halide

44
Q

Is the subsitution rxn more sensitive to substituents on the alpha or beta carbon

A

alpha carbon, but still senstive on beta carbon just not as much

45
Q

at what amnt of substituents attatched to the alpha or beta carbon will the reaction no longer happen?

A

on a tertiaty alpha or beta carbon

46
Q

Steric Hindrence

A

crowding of the alpha carbon by groups that are not H groups

47
Q

concerted rxn

A

all mechanistic steps happen at one, one intermediate

48
Q

stepwise reaction

A

more than one mechanistic step, more than one transition state

OChem 1 (8 decks)

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