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Chem 1002 > Midterm 1 > Flashcards

Midterm 1 Flashcards

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1
Q

What are substitution reactions?

A

One functional group substitutes for another

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2
Q

What is an elimination reaction?

A

Atoms or groups of atoms in adjacent carbons are eliminated as a small molecule
Saturated become unsaturated

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3
Q

What are addition reactions?

A

Opposite of elimination reactions

Double becomes single

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4
Q

What are nucleophiles and electrophiles?

A

Nucleophiles: attracted to positive charges (negatively charged)
Electrophiles: attracted to electrons (positively charged)
Most reactions happen when a nucleophile and electrophile interact

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5
Q

What are nucleophilic centres?

A

Lone pairs, negative charges, and multiple bonds

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6
Q

What are electrophilic centres?

A

Positive charges and positively polarized atoms

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7
Q

What are the two ways movement of electrons cause reactions?

A

1) a bond forms as a nucleophile and an electrophile interact (electrons in centre become barn)
2) bonding electrons move to an atom, breaking the bond, and the atom leaves

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8
Q

What occurs in nucleophilic substitution reactions?

A

A nucleophile attacks a substrate and creates a product and a leaving group

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9
Q

What are the two mechanisms of substitution reactions?

A

Sn2 - one step reaction where rate depends on concentrations of both
Sn1 - two step reaction. First step creates an intermediate carbocation which then reacts with the nucleophile. Rate is based on slowest step

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10
Q

What factors affect the SN1 reaction rate?

A
  1. Stability of the intermediate: tertiary is fastest

2. Strength of the leaving group: stronger bases = poor leaving group,

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11
Q

What are the two elimination mechanisms?

A

E2: rate depends on concentration of both, 1 step
E1: two steps, slow and fast

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12
Q

What is regioselectivity?

A

Placement of double bond
One is preferred over the other
Creates a major and a minor
The more highly substituted alkene is the major

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13
Q

What is stereo selectivity?

A

Cis or trans

Trans is generally major

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14
Q

How do you determine where the electronegative atom goes in an addition reaction?

A

Use markovnikovs rule: the less electronegative atom bonds to the C atom that have the greater number of H atoms

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15
Q

What occurs when you have chirality with addition reactions?

A

Nucleophile can attack from front or back so end up with 50/50 split S/R

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16
Q

Define spontaneous change

A

No action from outside the system is necessary
Occurs on it’s own
Naturally move only in spontaneous direction

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17
Q

Does spontaneous change = heat released?

A

Not always

Spontaneous change = energy released always

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18
Q

Define entropy

A

A measure of the disorder or randomness in a closed system
A quantitative measure of the amount of thermal energy not available to do work
The tendency for all matter and energy in the universe to evolve towards a state of inert uniformity

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19
Q

What is the Boltzmann equation?

A 
S = k ln W
K= 1.38 x 10^ -23 j/k
W= number of ways that state can be achieved
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20
Q

Why is low energy less probable?

A

Nature is striving towards a state of high entropy

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21
Q

Is entropy a state or path function?

A

State function

Path taken and rate are irrelevant

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22
Q

When is entropy greater than 0?

A 
Increase in enthalpy
Melting
Vaporizing
Making a solution
A reaction that produces an increased number of moles
Heating a substance
23
Q

Why is the entropy of melting greater than 0?

A

As goes from solid to liquid, becomes more disordered

24
Q

Why is the entropy of vaporizing greater than 0?

A

When going for liquid to gas, disorder increases

25
Q

Why is the entropy of making a solution greater than 0?

A

It is far more likely that the solutions mix evenly than layered as it has a higher entropy

26
Q

Why is the entropy of a redaction that produces an increased number of moles greater than 0?

A

More bonds are broken than made

27
Q

What is the equation for calculating 🔺S of a solution?

A

🔺S rxn = E(vi Si)
Vi = stochiometric coefficient of species i
Si = absolute entropy of species i

28
Q

When can the entropy of a system decrease?

A

Only if the entropy of the surroundings increases even more

29
Q

What must the entropy be for the reaction to be spontaneous?

A

🔺S > 0

30
Q

What is needed for a nonspontaneous process to take place?

A

Need outside action such as a change in p, T concentrations

Possibly but only if changing conditions

31
Q

What is the equation for 🔺S of the surroundings?

A

-🔺H system / T

32
Q

What is Gibbs free energy?

A

The maximum non-pV energy obtained from a system

🔺G = 🔺H - T🔺S

33
Q

When is Gibbs free energy greater than 0?

A 
H S G spontaneous
-  +  -  always
\+  -  +  never 
-   -  +-  at lower T
\+  +  +-  at higher T
34
Q

Is free energy a state or path function?

A

State function

Path and rate is irrelevant

35
Q

What is Q?

A

Reaction quotient

🔺G = 🔺Go + RT ln Q

36
Q

What happens to vapour pressure at equilibrium?

A

Rate of evaporation = rate of condensation

37
Q

What is a Clausius-Clapeyron?

A

ln(pvap)=-(🔺Hvap/R)(1/T)+(🔺Svap/R)

38
Q

What is a Clausius-Clapeyron pressure equation?

A

ln(p2) = ln(p1) + 🔺Hvap/R (1/t1-1/t2)

39
Q

What is troutons rule?

A

🔺S’vap = 🔺H’vap/Tb

40
Q

What is pyro metallurgy?

A

Production of metals from ores using heat

41
Q

What are elementary reactions?

A

The simplest steps in a reaction
Each involved bond making and breaking
Usually unimolecular or bimolecular

42
Q

What is the rate determining step?

A

The slowest elementary reaction in a multistep reaction

Determines overall rate of reaction

43
Q

What does a catalyst do?

A

Speeds up a reaction but is not consumed itself

Provides a different mechanism for the reaction to proceed

44
Q

What are the steps to heterogeneous catalysis?

A
  1. Absorption
  2. Migration across surface
  3. Reaction
  4. Desorption
45
Q

What is a thermal explosion?

A

As reaction proceeds T rises, k rides
Reaction goes faster t rises, k rises
BOOM
releases a large pressure wave

46
Q

What is a chain explosion?

A

Radicals contain unpaired electrons which are very reactive
1. Initiation step: radicals are produced
2. Propagation steps: no net radical production than branching occurs, number of radicals increases
More radicals = higher rates = more radicals = BOOM

47
Q

What is the rate law?

A

Expresses how the rate varies with concentrations of reactants
Rate = k[reactant]^n
First order k= s^-1
2nd order k= M^-1 s^-1

48
Q

What is the integrated rate law?

A

1st order: ln([A]/[A]o) = -kt

2nd order: 1/[A] = kt + 1/[A]o

49
Q

What is the half life?

A

1st order: t1/2 = 0.693/k

2nd order: t1/2 = 1/k[A]o

50
Q

What affects the reaction rate?

A
  1. Rate of collisions between A and B
  2. Fraction of collisions having correct orientation
  3. Fraction of collisions having sufficient energy to cause reaction
51
Q

What is the activation energy?

A

The energy required for a reaction to go to completetion

52
Q

What so the Arrhenius equation?

A

K = Ae^-Ea/RT

53
Q

What are the three most important types of organic reaction?

A

Substitution, elimination, addition

Chem 1002 (1 decks)

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