Midterm 1 Flashcards
(53 cards)
What are substitution reactions?
One functional group substitutes for another
What is an elimination reaction?
Atoms or groups of atoms in adjacent carbons are eliminated as a small molecule
Saturated become unsaturated
What are addition reactions?
Opposite of elimination reactions
Double becomes single
What are nucleophiles and electrophiles?
Nucleophiles: attracted to positive charges (negatively charged)
Electrophiles: attracted to electrons (positively charged)
Most reactions happen when a nucleophile and electrophile interact
What are nucleophilic centres?
Lone pairs, negative charges, and multiple bonds
What are electrophilic centres?
Positive charges and positively polarized atoms
What are the two ways movement of electrons cause reactions?
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
What occurs in nucleophilic substitution reactions?
A nucleophile attacks a substrate and creates a product and a leaving group
What are the two mechanisms of substitution reactions?
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
What factors affect the SN1 reaction rate?
- Stability of the intermediate: tertiary is fastest
2. Strength of the leaving group: stronger bases = poor leaving group,
What are the two elimination mechanisms?
E2: rate depends on concentration of both, 1 step
E1: two steps, slow and fast
What is regioselectivity?
Placement of double bond
One is preferred over the other
Creates a major and a minor
The more highly substituted alkene is the major
What is stereo selectivity?
Cis or trans
Trans is generally major
How do you determine where the electronegative atom goes in an addition reaction?
Use markovnikovs rule: the less electronegative atom bonds to the C atom that have the greater number of H atoms
What occurs when you have chirality with addition reactions?
Nucleophile can attack from front or back so end up with 50/50 split S/R
Define spontaneous change
No action from outside the system is necessary
Occurs on it’s own
Naturally move only in spontaneous direction
Does spontaneous change = heat released?
Not always
Spontaneous change = energy released always
Define entropy
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
What is the Boltzmann equation?
S = k ln W K= 1.38 x 10^ -23 j/k W= number of ways that state can be achieved
Why is low energy less probable?
Nature is striving towards a state of high entropy
Is entropy a state or path function?
State function
Path taken and rate are irrelevant
When is entropy greater than 0?
Increase in enthalpy Melting Vaporizing Making a solution A reaction that produces an increased number of moles Heating a substance
Why is the entropy of melting greater than 0?
As goes from solid to liquid, becomes more disordered
Why is the entropy of vaporizing greater than 0?
When going for liquid to gas, disorder increases
