Organic Reactions and Mechanisms of Organic Compounds

Question 1

2 classifications of ORGANIC REACTIONS

Answer 1

BASED ON:

1. net transformation
2. reaction mechanism

Question 2

WRITING EQUATIONS FOR ORGANIC REACTIONS

• general formula
• rules (2)

Answer 2

substrate + reagent ->(reaction conditions) products

REAGENT: can be written above arrow
REACTION CONDITION: may be written above or below arrow

Question 3

TYPES of ORGANIC REACTIONS (6)

Answer 3

1. Addition
2. Elimination
3. Substitution
4. Rearrangement
5. Oxidation
6. Reduction

Question 4

TYPES of ORGANIC REACTIONS

ADDITION (3)

Answer 4

• 2 reactants to form 1 new produst
• no atom leftover
• PI BOND disappears

Question 5

TYPES of ORGANIC REACTIONS

ELIMINATION (3)

Answer 5

• 1 reactant to form 2 or more products
• removal of atoms from a molecule
• PI BOND appears

Question 6

TYPES of ORGANIC REACTIONS

SUBSTITUTION (2)

Answer 6

• 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

Question 7

TYPES of ORGANIC REACTIONS

REARRANGEMENT (2)

Answer 7

• reorganization of atom or groups of atom WITHIN molecule
• forms ISOMERS of original molecule

Question 8

TYPES of ORGANIC REACTIONS

OXIDATION (2)

Answer 8

• gains O
• loses H

Question 9

TYPES of ORGANIC REACTIONS

REDUCTION (2)

Answer 9

• loses O
• gains H

Question 10

WRITING EQUATIONS FOR REACTION MECHANISM

• general formula

Answer 10

substrate + reagent ->(reaction conditions) intermediate…
->(route A) product A
->(route B) product B

Question 11

REACTION MECHANISM

• main definition
• 2 processes
• 2 properties per each and their definition

Answer 11

• 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)

Question 12

Which are stronger:

• pi bonds
• sigma bonds?

Answer 12

sigma bonds

Question 13

What type of ARROW is used for the following:

1. movement of 2 electrons
2. movement of 1 electron

Answer 13

1. double-headed arrow
2. one-headed arrow

Question 14

2 TYPES of BOND CLEAVAGE

and differences in terms of:

• bond-breaking symmetry
• how many electrons is moved?
• formation of what + definition

Answer 14

BC
1. Homolysis
- symmetrical bond-breaking
- 1 electron
- FREE RADICAL FORMATION - each product gets an electron upon breaking

2. Heterolysis
   - unsymmetrical bond-breaking
   - 2 electrons
   - CATION AND ANION FORMATION - one product gets both electrons upon breaking

Question 15

2 TYPES of BOND FORMATION

and differences in terms of:

• main definition

Answer 15

BF
1. Homogenic Bond Formation
- each free-radical fragment donates 1 electron to form bond

2. Heterogenic Bond Formation
   - electron-rich fragments shares 2 electrons to form a bond

Question 16

3 TYPES of REAGENTS

Answer 16

1. Nucleophiles
2. Electrophiles
3. Free Radicals

Question 17

TYPES OF REAGENTS - Nucleophiles

• other term
• seeks??
• Lewis base or acid?

Answer 17

• nucleus-loving (+)
• seeks e-poor sites
• Lewis base (e- pair donor)

Question 18

TYPES OF REAGENTS - Electrophiles

• other term
• seeks??
• Lewis base or acid?

Answer 18

• electron-loving (-)
• seeks e-rich sites
• Lewis base (e- pair acceptor)

Question 19

TYPES OF REAGENTS - Free Radicals

• other term
• distinguishing feature
• reactivity

Answer 19

• neutral species
• singular e- on one side
• very reactive

Question 20

HOW TO DIFFERENTIATE THE REAGENTS

1. Nucleophile (3)
2. Electrophile (2)
3. Free radicals (1)

Answer 20

1. Nucleophile
   - lone pairs
   - multiple bonds (double/triple bonded)
   - negative charge (-)
2. Electrophile
   - presence of N, O, or X (halogen) in molecule #1, MAKES the carbon in molecule #2 be electrophilic
   - positive/neutral charge
3. Free Radicals
   - singular e- on one side

Question 21

2 TYPES OF REACTIONS

Answer 21

1. Non-polar reaction
2. Polar reaction

Question 22

TYPES OF REACTIONS - NON-POLAR REACTION

• other term
• involves what mechanism
• produces what reactive intermediate
• occurs in?
• initiated by presence of (3)?

Answer 22

• 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

Question 23

TYPES OF REACTIONS - POLAR REACTION

• other term
• involves what mechanism
• produces what reactive intermediate
• occurs in?
• 2 classifications

Answer 23

• IONIC reaction
• involves HETEROLYTIC MECHANISMS
• produces IONS as reactive intermediates
• occurs in polar solvents (stabilizes ions)
• classified into NUCLEOPHILIC and ELECTROPHILIC reactions

Question 24

POLAR REACTION - USE OF CURVED ARROWS

3 main rules

Answer 24

1. movement of e- is from nucleophilic source to electrophilic source
2. total charge of REACTANTS is = to total charge of PRODUCTS
3. The octet rule is always followed

Question 25

POLAR REACTION - USE OF CURVED ARROWS RULE CHANGES in charge in Nucleophile and Electrophile

Answer 25

1. If N is - charged (R) -> N becomes neutral (P) 2. If N is neutral (R) -> N becomes + charged (P) 3. 1. If E is + charged (R) -> E becomes neutral (P) 4. If E is neutral (R) -> E becomes - charged (P) *(R) - reactants *(P) - products

Question 26

EQUILIBRIUM CONSTANT - main definition - only for... - interpretation of the following: Keq > 1 Keq = 1 Keq < 1

Answer 26

- tells which side of the reaction is energetically favoured - only for gas and aq Forward Reaction Equilibrium Reaction Backward Reaction

Question 27

GIBBS FREE ENERGY CHANGE - interpretation for the ff: +ΔG -ΔG ΔG°

Answer 27

+ΔG (endergonic) - non-spontaneous -ΔG (exergonic) - spontaneous ΔG° = ΔH° - TΔS°

Question 28

ENTHALPY CHANGE - interpretation for the ff: +ΔH -ΔH IN TERMS OF... 1. bond strength 2. bond stability 3. bond formation or breaking?

Answer 28

+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

Question 29

3 qualifications for a CHEMICAL REACTION to occur and what is the THEORY that governs this?

Answer 29

COLLISION THEORY OF REACTION RATES - needs collision of particles with: 1. sufficient energy 2. proper orientation 3. enough concentration

Question 30

ENTROPY CHANGE - interpretation for the ff: +ΔS -ΔS and amount as phase state changes

Answer 30

+ΔS - increased disorder - A -> B + C -ΔS - decreased disorder - A + B -> C S -> L -> G (increasing ΔS) G->L->S (decreasing ΔS)

Question 31

what are REACTION ENERGY DIAGRAMS

Answer 31

graphical representation of energy changes during a reaction

Question 32

REACTIVE ENERGY DIAGRAMS gives information on...? (4)

Answer 32

1. relative rates 2. thermodynamics 3. number of steps 4. rate determining step

Question 33

REACTIVE ENERGY DIAGRAMS 3 types

Answer 33

1. One-step 2. Multi-step reactions 3. Catalyzed reactions

Question 34

REACTIVE ENERGY DIAGRAMS--ONE-STEP - other term - main definition - structure of transition state - main formulas (2)

Answer 34

# 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

Question 35

What is a TRANSITION STATE ? (2) and what postulate does its STRUCTURE follow?

Answer 35

- highest energy state - unstable and cannot be isolated Hammond Postulate (structure of TS resembles structure of nearest stable species)

Question 36

What is ACTIVATION ENERGY ? (1)

Answer 36

minimum amount of energy to break the bonds of the reactants

Question 37

REACTION ENERGY DIAGRAMS FOR 1. Low/High Energy 2. +ΔH / -ΔH and which of the 4 combinations is the MOST FAVOURABLE?

Answer 37

Low Ea - Fast Reaction Exothermic - spontaneous

Question 38

REACTIVE ENERGY DIAGRAMS--MULTI-STEP - main definition - 3 steps

Answer 38

- reactions w/ 2 or more steps (bond breaking and formation IS NOT simultaneous) 1. Bond breaking 2. Formation of reaction intermediate (formed in 1, consumed in 3) 3. Bond formation

Question 39

what are REACTION INTERMEDIATES (2)

Answer 39

- not the final product - more stable than transition state but cant be isolated

Question 40

what is used to determine the STEP WITH THE HIGHEST Ea

Answer 40

RATE DETERMINING STEP - finds slowest reaction rate

Question 41

REACTIVE ENERGY DIAGRAMS--CATALYZED - lowers/highers what? - main function - series of?

Answer 41

- lowers Ea - to speed up chemical reaction - series of smaller chemical reactions