Organic Reactions and Mechanisms of Organic Compounds Flashcards
2 classifications of ORGANIC REACTIONS
BASED ON:
- net transformation
- reaction mechanism
WRITING EQUATIONS FOR ORGANIC REACTIONS
- general formula
- rules (2)
substrate + reagent ->(reaction conditions) products
REAGENT: can be written above arrow
REACTION CONDITION: may be written above or below arrow
TYPES of ORGANIC REACTIONS (6)
- Addition
- Elimination
- Substitution
- Rearrangement
- Oxidation
- Reduction
TYPES of ORGANIC REACTIONS
ADDITION (3)
- 2 reactants to form 1 new produst
- no atom leftover
- PI BOND disappears
TYPES of ORGANIC REACTIONS
ELIMINATION (3)
- 1 reactant to form 2 or more products
- removal of atoms from a molecule
- PI BOND appears
TYPES of ORGANIC REACTIONS
SUBSTITUTION (2)
- replacement of atom or groups of atom
- or molecules, each from substrate and reagent, nag exchange *
*not rearrangement if it DOES NOT form a positional isomer
TYPES of ORGANIC REACTIONS
REARRANGEMENT (2)
- reorganization of atom or groups of atom WITHIN molecule
- forms ISOMERS of original molecule
TYPES of ORGANIC REACTIONS
OXIDATION (2)
- gains O
- loses H
TYPES of ORGANIC REACTIONS
REDUCTION (2)
- loses O
- gains H
WRITING EQUATIONS FOR REACTION MECHANISM
- general formula
substrate + reagent ->(reaction conditions) intermediate…
->(route A) product A
->(route B) product B
REACTION MECHANISM
- main definition
- 2 processes
- 2 properties per each and their definition
- a detailed description of a chemical reaction
ELECTRON PUSHING
- bond cleavage
- bond formation
REACTION ENERGY DIAGRAMS
- kinetics (relatve rates of each step)
- thermodynamics (favoured steps)
Which are stronger:
- pi bonds
- sigma bonds?
sigma bonds
What type of ARROW is used for the following:
- movement of 2 electrons
- movement of 1 electron
- double-headed arrow
- one-headed arrow
2 TYPES of BOND CLEAVAGE
and differences in terms of:
- bond-breaking symmetry
- how many electrons is moved?
- formation of what + definition
BC
1. Homolysis
- symmetrical bond-breaking
- 1 electron
- FREE RADICAL FORMATION - each product gets an electron upon breaking
- Heterolysis
- unsymmetrical bond-breaking
- 2 electrons
- CATION AND ANION FORMATION - one product gets both electrons upon breaking
2 TYPES of BOND FORMATION
and differences in terms of:
- main definition
BF
1. Homogenic Bond Formation
- each free-radical fragment donates 1 electron to form bond
- Heterogenic Bond Formation
- electron-rich fragments shares 2 electrons to form a bond
3 TYPES of REAGENTS
- Nucleophiles
- Electrophiles
- Free Radicals
TYPES OF REAGENTS - Nucleophiles
- other term
- seeks??
- Lewis base or acid?
- nucleus-loving (+)
- seeks e-poor sites
- Lewis base (e- pair donor)
TYPES OF REAGENTS - Electrophiles
- other term
- seeks??
- Lewis base or acid?
- electron-loving (-)
- seeks e-rich sites
- Lewis base (e- pair acceptor)
TYPES OF REAGENTS - Free Radicals
- other term
- distinguishing feature
- reactivity
- neutral species
- singular e- on one side
- very reactive
HOW TO DIFFERENTIATE THE REAGENTS
- Nucleophile (3)
- Electrophile (2)
- Free radicals (1)
- Nucleophile
- lone pairs
- multiple bonds (double/triple bonded)
- negative charge (-) - Electrophile
- presence of N, O, or X (halogen) in molecule #1, MAKES the carbon in molecule #2 be electrophilic
- positive/neutral charge - Free Radicals
- singular e- on one side
2 TYPES OF REACTIONS
- Non-polar reaction
- Polar reaction
TYPES OF REACTIONS - NON-POLAR REACTION
- other term
- involves what mechanism
- produces what reactive intermediate
- occurs in?
- initiated by presence of (3)?
- FREE RADICAL reaction
- involves HOMOLYTIC MECHANISMS
- produces FREE-RADICALS as reactive intermediates
- occurs in non-polar solvents (g & aq)
- light, heat, and free-radical initiators
TYPES OF REACTIONS - POLAR REACTION
- other term
- involves what mechanism
- produces what reactive intermediate
- occurs in?
- 2 classifications
- IONIC reaction
- involves HETEROLYTIC MECHANISMS
- produces IONS as reactive intermediates
- occurs in polar solvents (stabilizes ions)
- classified into NUCLEOPHILIC and ELECTROPHILIC reactions
POLAR REACTION - USE OF CURVED ARROWS
3 main rules
- movement of e- is from nucleophilic source to electrophilic source
- total charge of REACTANTS is = to total charge of PRODUCTS
- The octet rule is always followed
POLAR REACTION - USE OF CURVED ARROWS
RULE CHANGES in charge in Nucleophile and Electrophile
- If N is - charged (R) -> N becomes neutral (P)
- If N is neutral (R) -> N becomes + charged (P)
- If E is + charged (R) -> E becomes neutral (P)
- If E is neutral (R) -> E becomes - charged (P)
*(R) - reactants
*(P) - products
EQUILIBRIUM CONSTANT
- main definition
- only for…
- interpretation of the following:
Keq > 1
Keq = 1
Keq < 1
- tells which side of the reaction is energetically favoured
- only for gas and aq
Forward Reaction
Equilibrium Reaction
Backward Reaction
GIBBS FREE ENERGY CHANGE
- interpretation for the ff:
+ΔG
-ΔG
ΔG°
+ΔG (endergonic) - non-spontaneous
-ΔG (exergonic) - spontaneous
ΔG° = ΔH° - TΔS°
ENTHALPY CHANGE
- interpretation for the ff:
+ΔH
-ΔH
IN TERMS OF…
1. bond strength
2. bond stability
3. bond formation or breaking?
+ΔH (endothermic)
1. bonds in reactants are STRONGER and more STABLE
2. breaking of bonds
-ΔH (exothermic)
1. bonds in products are STRONGER and more STABLE
2. formation of bonds
3 qualifications for a CHEMICAL REACTION to occur
and what is the THEORY that governs this?
COLLISION THEORY OF REACTION RATES
- needs collision of particles with:
- sufficient energy
- proper orientation
- enough concentration
ENTROPY CHANGE
- interpretation for the ff:
+ΔS
-ΔS
and amount as phase state changes
+ΔS
- increased disorder
- A -> B + C
-ΔS
- decreased disorder
- A + B -> C
S -> L -> G (increasing ΔS)
G->L->S (decreasing ΔS)
what are REACTION ENERGY DIAGRAMS
graphical representation of energy changes during a reaction
REACTIVE ENERGY DIAGRAMS
gives information on…? (4)
- relative rates
- thermodynamics
- number of steps
- rate determining step
REACTIVE ENERGY DIAGRAMS
3 types
- One-step
- Multi-step reactions
- Catalyzed reactions
REACTIVE ENERGY DIAGRAMS–ONE-STEP
- other term
- main definition
- structure of transition state
- main formulas (2)
of intermediates = (# of transition state)-1
- Concerted Reactions
- bond BREAKING & FORMATION occurs simultaneously
[A—-B—-C] ‡ (double dagger)
no. of transition state = no. of steps
no. of intermediates = no. of transition state - 1
What is a TRANSITION STATE ? (2)
and what postulate does its STRUCTURE follow?
- highest energy state
- unstable and cannot be isolated
Hammond Postulate (structure of TS resembles structure of nearest stable species)
What is ACTIVATION ENERGY ? (1)
minimum amount of energy to break the bonds of the reactants
REACTION ENERGY DIAGRAMS FOR
- Low/High Energy
- +ΔH / -ΔH
and which of the 4 combinations is the MOST FAVOURABLE?
Low Ea - Fast Reaction
Exothermic - spontaneous
REACTIVE ENERGY DIAGRAMS–MULTI-STEP
- main definition
- 3 steps
- reactions w/ 2 or more steps (bond breaking and formation IS NOT simultaneous)
- Bond breaking
- Formation of reaction intermediate (formed in 1, consumed in 3)
- Bond formation
what are REACTION INTERMEDIATES (2)
- not the final product
- more stable than transition state but cant be isolated
what is used to determine the STEP WITH THE HIGHEST Ea
RATE DETERMINING STEP
- finds slowest reaction rate
REACTIVE ENERGY DIAGRAMS–CATALYZED
- lowers/highers what?
- main function
- series of?
- lowers Ea
- to speed up chemical reaction
- series of smaller chemical reactions
