Kinetics II
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What is the rate equation?
• k[A]^m[B]^n
how will a conc-rate graph look for a 0 order reaction?
• Flat line (m of 0)
How will a con-rate graph look for a 1st order reaction?
• straight line going through the origin (positive m)
How will a con-rate graph look for a 2nd order reaction?
• exponential graph with a positive m
What does it tell us if half lives of a conc-time graph are constant?
its 1st order
What does it tell us if half lives of a conc-time graph are rapidly increasing (or vary very weirdly?)
its 2nd order
What does it tell us if half lives of a conc-time graph are a straight line with a negative m?
it is 0 order
what are the units of an overall reaction of 2nd order?
mol^-1dm^3s^-1
what are the units of an overall reaction of 1st order?
s^-1
what are the units of an overall reaction of 3rd order?
• mol^-2dm^6s^-1
give some key points of Sn1 reactions?
• only have 1 molecule or ion in the rate determining step (rate equation) • tertiary or secondary haloalkanes react through this mechanism
Describe Sn1 reactions
• curly arrow from middle of C-X bond to X- • forms a carbocation with a X- • OH- ion attacks carbocation (which will be a positive)
Describe Sn2 reactions
• forms an intermediate from nucleophillic substitution (kind of like a halogen and OH- competing for the spot) • HAPPENS IN ONE STEP
Give some key points of Sn2 reactions
• only 1 rate determining step • have 2 molecules or ions in the rate determining step. ( rate equation)
Why do tertiary haloalkanes proceed via Sn1 reactions?
• Because there is less space around their alkyl groups (they’re larger) for nucleophiles to attack,