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Organic Chemistry > Chemical reactivity and mechanisms > Flashcards

Chemical reactivity and mechanisms Flashcards

1
Q

Heterolytic bond cleavage

A

Results in forming ions & use only a single head curved arrow

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2
Q

Enthaply (ΔH)

A

Heat at constant pressure

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2
Q

Bond dissociation energy

A

The energy required to break a covalent bond through hommolytic bond cleavage

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3
Q

Homolytic Bond cleavage

A

Results in forming two uncharged radicals (Use two half curved arrows)

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5
Q

The ΔH0 is known as the ______________

A

Standard bond dissociation (under standard conditions like 1 atm)

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6
Q

Heat of reaction

A

The total change in enthaply for a reaction

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7
Q

Entropy

A

Measure of disorder associated with a system

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8
Q

Spontaneous reaction

A

Increases total entropy (ΔStot = Ssys + Ssurr) (ΔStotal has to be positive for a reaction to be spontaneous)

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9
Q

Between liquids, solids, & gases list it in increasing entropy

A

Ssolid < Sliquid gas (from least to greatest)

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10
Q

Under constant pressure what is the equation used for ΔSsurr ?

A

ΔSsurr = -ΔHsys / T

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11
Q

What is the equation for Gibbs free energy?

A

ΔG = ΔH - TΔS (ΔG must be negative for a reaction to be spontaneous)

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12
Q

Exergonic

A

A reaction where ΔG is negative

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13
Q

Endergonic

A

A reaction where ΔG is positive

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14
Q

Equilibrium constant (Keq)

A

Keq = [Products] /[Reactants]

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15
Q

Equation relating equilibrium constant to ΔG

A

ΔG = -RTlnKeq

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16
Q

With the equation relating ΔG & Keq if ΔG is negative then the __________ are favored (Keq > 1) & if ΔG is positive the _________ will be favored (Keq < 1)

A

Products, Reactnats

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17
Q

What is the rate equation?

A

R = k[Reactants] (R = k[A] *[B]*)

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18
Q

What are the factors that affect the rate constant?

A
  1. Energy Activation (Ea)
  2. Temperature
  3. Steric Considerations
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19
Q

How does Ea (activation energy) affect the rate of a reaction?

A

The activation energy is the minium energy required for a reaction to occur so the lower the Ea the faster the reaction & the larger the Ea the slower the reaction

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20
Q

How does the temperature affect the rate of a reaction?

A

The rate constant (k) is directly proportional to temp. & the rate of a reaction so increase the temp will increase the rate constant & speed up the rate of the reaction & vis versa when decreased

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21
Q

Catalysts

A

Speeds up the reaction without being consumed (Enzymes are a type of calalysts)

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22
Q

Transition state on a energy diagram

A

Highest peaks on the graph

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23
Q

Intermediate on a energy diagram

A

Peaks where it concaves up on the graph

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24
Q

The transition state is where the ____________ occurs where bonds are broken & formed

A

Reaction

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25
What is the Hammond Postulate?
States that if the reactants are close in energy to the transition state then the transition state will look like the reactants (exothermic reaction) & if the products are close in energy to the transition state then the transition state will look like the products (endothermic reaction)
26
Nucleophile
Reacts with a positive charged atom & donates electrons (has a high electron density)
27
Electrophile
Reacts with a negative charged atom & accepts electrons (Low electron density)
28
A ____________ shows how a reaction takes place using a curved arrows to show the flow of electrons (The tail shows where the electrons coming from & the head shows where its going to)
Mechanism
29
What are the patterns of a mechanism?
1. Nucleophilic Attack 2. Loss of a leaving group 3. Proton Transfer 4. Rearrangments
30
Nucleophilic Attack
A nuclepphile attacking (donating electrons) to an electrophile
31
Loss of a leaving group
32
Proton Transfer
For a compound to lose a proton (transfer a proton (H) a base must be present to deprontonate the compound)
33
Rearrangment (Carbocation arrangement)
Carbocation are stabilized by neigboring alkyl groups & a prcoess calles hyperconjugation- stablizes the P orbitial
34
What are the two types of rearrangments to stablize the carbocations?
1. Hydride shift (involves moving a hydrogen) 2. Methyl shift (involves moving a methyl group)
35
The terms primary, secondary, tertiary, represents the number of ________ groups attached directly to the positively charged atom
Alkyl
36
\_\_\_\_\_\_\_\_\_\_\_ carbocation are the most stable, & __________ are the least stable (secondary carbocation is in between the two)
Tertiary, primary
37
For a mehyl or hydride shift to occur they must be attacthed to a carbon atom that is ____________ to the carbocation
Adjacent
38
All mechanism are just a combination of the \_\_\_\_\_\_\_\_\_\_
4 patterns
39
When drawing the curved arrow the tail must either be on a bond or _________ & can never be on a \_\_\_\_\_\_\_\_\_\_
Lone pair, positive charge
40
The head of the curved arrow shows where the electrons are going to form a _________ or \_\_\_\_\_\_\_\_\_
Bond or lone pair (Have to make sure dont break the octect rule)
41
When predicting if a carbocation rearrangement (shift) can occur must determine wheteher the carbocation can become more ________ if a methyl or hydride shift was to occur
Stable
42
Reversible arrows
Equilibrium arrows
43
Irreverisble reaction arrows
Forward arrows
44
A reversible arrow is used if the nucleophile is capable of functioning as a _____________ after the nucleophilic attack
A good leaving group
45
A irrversible arrow is used if the nucleophile is a \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
Poor leaving group
46
For a loss of a leaving group a reversible arrow is mostly used for the reaction but its used only if the leaving group is capable of functioning as a \_\_\_\_\_\_\_\_\_\_\_\_\_
Good nucleophile
47
For a proton transer they are mostly drawn with a reversible arrow if the ________ difference is low
pKa
48
Irreversible arrows are used for a proton transfer when the pKa difference is greater than \_\_\_\_\_\_
10 pKa
49
Carbocation rearrangment are always drawn with an __________________ arrow
Irreversible arrow (Beacuse stabilzing a secondary carbocation into a tertiary one)
50
Free energy diagram gives us information on the ____________ & ________ of a reaction
Spontaneity & Rate of reaction
51
Stability & reactivity have a ___________ relationship
Inverse relationship (increase the stability decreases the reactivity & vis versa)
52
What are the 4 common indicators of a compound being reactive?
1. Formal charges 2. net dipoles (partial charges) 3. π bonds (have a good source of free electrons & wants give away) 4. Steric affect (Ring strains)
53
Negative charged atoms are called \_\_\_\_\_\_\_\_\_\_\_\_\_
Nucleophiles (donates electrons)
54
Positive charged atoms are called \_\_\_\_\_\_\_\_\_\_\_
Electrophiles (Accepts electrons)
55
The side of the dipole with the _______________ preference can be used to predict nucleophile or electrophile whenever there is no formal charges present
Highest bond (whatever atom can form the most bonds)
56
If a compound is not __________ then its neither nucleophile or electrophile
Reactive
57
\_\_\_\_\_\_\_\_\_\_\_\_\_ can be both a nucleophile or electrophile depending on the atom its reacting with
Water
58
Reactive molecules react to become more ___________ & share two electrons
Stable
59
Electrons flow from regions of ____________ electron denisty to regions of \_\_\_\_\_\_\_\_\_\_\_\_\_\_electron denisty
High electron denisty (Nucleophile) , low electron density (Electrophile)
60
\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ always attacks ___________ & the curved arrows shows 2 electrons being shared & an arrow will then be repalced with a sigma bond & bond breaking is only needed to protect the octect rule
Nucleophile, electrophile
61
Ring expansion (a type of carbocation rearrangment)
Occurs when a carbocation is adjacent to a 3,4,5 or small ring & turns it into a larger ring

Organic Chemistry (47 decks)

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