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Final

CHEM 210 Study Guide - Final Guide: Stage Name, Acid Dissociation Constant, Protic SolventPremium


Department
Chemistry
Course Code
CHEM 210
Professor
Kathleen Nolta
Study Guide
Final

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Chem 210: Structure and Reactivity - Lecture 12: Energy Diagrams
Anatomy of an Energy Diagram
Energy = G (E) - relative
Progress - bidirectional
SM = starting materials
P = products
Reaction is in steps (not time)
Ea (∆G≠) = transition state
Distance from valley to peak
Bonds breaking/ forming
> 0, always invest energy
Kinetic variable: high “humps” = slow step
Depends on Ea (activation energy) inversely
Rate Determining Step (RDS): the step with the highest transition state.
∆G: energy gained or lost
Valley to valley
∆G step: end of step - beginning
∆G rxn: product - starting material
Nucleophilic Substitution Reactions
Electrophiles: “electron seeking” atoms that have room to accept a pair of electrons
Nucleophiles: “nucleus seeking” atoms that have a pair of electrons to donate.
Three factors to consider to see if a reaction is likely:
Look at structure
Must be electron donor and acceptor present
The position of equilibrium between the reactants and products
The mechanism of the reaction, the details of the bond breaking and bond making that must
take place to go from reactants to products
Bonds break and form at the same time for maximum stability
Leaving group: a stable species that can be detached from a molecule in a bond - breaking
step.
One sided attack of nucleophile inverts all three stereochemical bonds.
Transition state: includes partial charges, indicates the state of the molecule between reaction
steps.
Electronic Addition Reactions:
A pi bond becomes two new bonds
Occurs only in double or triple bonds
Variation in bonding sites leads to regioisomers
Differences in energy diagrams

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Chem 210: Structure and Reactivity - Lecture 13: Energy and EA
Energy Diagrams with Competing Reaction Paths
Thermodynamic considerations:
Lowest G state means the most stable product
This stands for reversible systems as well
Kinetic considerations
Lowest activation energy, fastest RDS: favored product
Irreversible
Strong acid - kinetic control
Regioisomers and Regioselection
Two possible outcomes for every electronic addition reaction
More stable carbocation forms faster -- major product!
Substitution: the number of Carbons attached to central carbon
Resonance effect stabilizes Cs best
Resonance > 3 carbons > 2 carbons > 1 carbons
If all C’s identical, a single product connectivity is possible
If C’s are different but have the same stability, there will be an equal regiomix of products.
Chem 210: Structure and Reactivity - Lecture 14: Electronic Addition
Electronic Addition: strong acid
Step 1: H+ transfer
Pi bond becomes new sigma bond to H+
The other C (of the pi bond) is a C+ (carbocation)
Step 2: Complexation
Very fast
C+ is attacked
Simplest additions: H-X
Predicting Products
Are the Cs chemically identical?
If yes, single product connectivity
If no, regioisomers form (different connectivity)
Are the Cs equally stable as C+s?
If yes, regiomix (equal numbers)
If no, regioselection (one is formed)

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What Makes a C+ Stable?
If 1, 2, or 3 are alkyl groups, those bonds offer stabilizing e- rich umbrella
Resonance makes C+ more stable, lower in energy, and faster to form
Variation in Acid Chosen
If acid isn’t strong enough, an acid catalyst is required
H2SO4 is a good one
The real acid will be a protenated version of the original
This causes a third clean up step in the reaction to get rid of extra hydrogen
Chem 210: Structure and Reactivity - Lecture 15: Electronic Addition and NMR
Electronic Addition Reactions
Energy diagrams
Kinetics are predicted based on C+ stability
RDS is the formation of the carbocation
Thermodynamics are impossible to quantify
Acid Catalyzed Reactions
Can be made to add to a pi bond IF they can be made more acidic
Protenates acid to make stronger
C-NMR
The number of distinct or different carbons in a compound
On a C-NMR graph, each peak represents a different signal, or different carbon
Can provide hints for connectivity
H-NMR
The number of distinct hydrogens in a compound
On an H-NMR graph, each peak represents a different hydrogen
Each peak gives you the number of each type
Can be displayed as a number or as a ratio
Ratio contains the same number of values as the number of different hydrogens
For each different hydrogen, list how many hydrogens there are of each type
Nomenclature
Naming compounds defines them
IUPAC: a systematic approach to naming
Based on the main chain
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