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Complete organic chemistry notes, Study notes of Organic Chemistry

American University of Puerto Rico (AUPR)Organic Chemistry

Complete and schematic organic chemistry notes

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Organic Chemistry II Review Jasperse Basic Mechanism Principles

1

Reaction Mechanisms (see p. 310)

A. Recognizing/Classifying as Radical, Cationic, or Anionic

1. Radical

§ initiation requires both energy (either hv or Δ) and a weak, breakable heteroatom-heteroatom

bond

o Cl-Cl, Br-Br, O-O (peroxide), N-Br, etc..

2 Guides for That are Usually Reliable:

hv à radical mechanism

peroxides à radical mechanism

2. Anionic

§ a strong anion/base appears in the recipe

§ no strong acids should appear in the recipe

§ mechanisms should involve anionic intermediates and reactants, not strongly cationic ones

• (except for do-nothing spectators like metal cations)

§ The first step in the mechanism will involve the strong anion/base that appears in the recipe

3. Cationic

§ a strong acid/electrophile appears in the recipe

§ no strong anion/base should appear in the recipe

§ mechanisms should involve cationic intermediates and reactants, not strongly anionic ones

• (except for do-nothing spectators like halide or hydrogen sulfate anions)

§ The first step in the mechanism will involve the acid that appears in the recipe. The last step

will often involve a deprotonation step. Often the main step occurs in between the proton-

on and proton-off steps

B. Miscellaneous Mechanism Tips

1. Keep track of hydrogens on reacting carbons

2. Each step in a mechanism must balance

3. The types of intermediates involved (cation, anion, or radical) should be consistent with

the reaction classification above

a. If the reaction is cationic, don’t show anionic intermediates

b. If the reaction is anionic, don’t show cationic intermediates

4. Usually conditions are ionic.

5. Use a reactive species, whether strong anion or an acid, to start the first step

a. If acidic, first step will involve protonation of the organic

b. If anionic, the first step will involve the anion attacking the organic.

6. While it isn’t always easy to figure out what is a good mechanism, you should often be

able to eliminate an unreasonable mechanism.

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Organic Chemistry II Review Jasperse Basic Mechanism Principles 1

Reaction Mechanisms (see p. 310)

A. Recognizing/Classifying as Radical, Cationic, or Anionic

1. Radical

§ initiation requires both energy (either hv or Δ) and a weak, breakable heteroatom-heteroatom

bond

o Cl-Cl, Br-Br, O-O (peroxide), N-Br, etc..

2 Guides for That are Usually Reliable:

hv à radical mechanism

peroxides à radical mechanism

2. Anionic

§ a strong anion/base appears in the recipe

§ no strong acids should appear in the recipe

§ mechanisms should involve anionic intermediates and reactants, not strongly cationic ones

(except for do-nothing spectators like metal cations)

§ The first step in the mechanism will involve the strong anion/base that appears in the recipe

3. Cationic

§ a strong acid/electrophile appears in the recipe

§ no strong anion/base should appear in the recipe

§ mechanisms should involve cationic intermediates and reactants, not strongly anionic ones

(except for do-nothing spectators like halide or hydrogen sulfate anions)

§ The first step in the mechanism will involve the acid that appears in the recipe. The last step

will often involve a deprotonation step. Often the main step occurs in between the proton-

on and proton-off steps

B. Miscellaneous Mechanism Tips

1. Keep track of hydrogens on reacting carbons

2. Each step in a mechanism must balance

3. The types of intermediates involved (cation, anion, or radical) should be consistent with

the reaction classification above

a. If the reaction is cationic, don’t show anionic intermediates

b. If the reaction is anionic, don’t show cationic intermediates

4. Usually conditions are ionic.

5. Use a reactive species, whether strong anion or an acid, to start the first step

a. If acidic, first step will involve protonation of the organic

b. If anionic, the first step will involve the anion attacking the organic.

6. While it isn’t always easy to figure out what is a good mechanism, you should often be

able to eliminate an unreasonable mechanism.

Organic Chemistry II Review Jasperse Basic Mechanism Principles 2

Some Arrow-Pushing Guidelines (Section 1.14)

1. Arrows follow electron movement.

2. Some rules for the appearance of arrows

The arrow must begin from the electron source. There are two sources:

a. An atom (which must have a lone pair to give)

b. A bond pair (an old bond that breaks)

An arrow must always point directly to an atom, because when electrons move, they

always go to some new atom.

3. Ignore any Spectator Atoms. Any metal atom is always a “spectator”

When you have a metal spectator atom, realize that the non-metal next to it must have

negative charge

4. Draw all H’s on any Atom Whose Bonding Changes

5. Draw all lone-pairs on any Atom whose bonding changes

6. KEY ON BOND CHANGES. Any two-electron bond that changes (either made or

broken) must have an arrow to illustrate:

where it came from (new bond made) or
an arrow showing where it goes to (old bond broken)

7. Watch for Formal Charges and Changes in Formal Charge

If an atom’s charge gets more positive Þ it’s donating/losing an electron pair Þ arrow

must emanate from that atom or one of it’s associated bonds. There are two “more

positive” transactions:

When an anion becomes neutral. In this case, an arrow will emanate from the

atom. The atom has donated a lone pair which becomes a bond pair.

When a neutral atom becomes cationic. In this case, the atom will be losing a

bond pair, so the arrow should emanate from the bond rather than from the atom.

If an atom’s charge gets more negative Þ it’s accepting an electron pair Þ an arrow must

point to that atom. Ordinarily the arrow will have started from a bond and will point to

the atom.

8. When bonds change, but Formal Charge Doesn’t Change, A “Substitution” is Involved

Often an atom gives up an old bond and replaces it with a new bond. This is

“substitution”.

In this case, there will be an incoming arrow pointing directly at the atom (to illustrate

formation of the new bond), and an outgoing arrow emanating from the old bond that

breaks

Organic Chemistry II Review Jasperse Some Fundamental Stability/Reactivity Principles 2

Stability/Reactivity/Selectivity Principles

1. Reactant Stability/Reactivity : The more stable the reactant, the less reactive it will be. In

terms of rates, this means that the more stable the reactant, the slower it will react. (The concept

here is that the more stable the reactant, the more content it is to stay as is, and the less

motivated it is to react and change into something different)

Key note: Often the “reactant” that’s relevant in this context will not be the original

reactant of the reaction, but will be the “reactant” involved in the rate determining step.

Basicity

Why: As anion stability increases from A to D, the reactivity decreases

Nucleophilicity

Why: As anion stability increases from A to D, the reactivity decreases

Nucleophilicity

Why: As anion stability increases from A to D, the reactivity decreases

Reactivity toward alkanes via radical halogenation

F

2

> Cl

2

> Br

2

> I

2

because F• > Cl• > Br• > I•

Why: Chlorine is more reactive the bromine because chlorine radical is less

stable then bromine radical.

Electrophilicity (Reactivity in S N

2, S

N

1, E2, E1 Reactions)

Why: As carbon-halogen bond stability increases, the reactivity decreases

CH

2

Na NHNa ONa ONa

O

A

B

C

D

CH

2

Na NHNa ONa ONa

O

A

B

C

D

SeNa SNa ONa ONa

O

A

B

C

D

I

Br Cl

Organic Chemistry II Review Jasperse Some Fundamental Stability/Reactivity Principles 3

2. Product Stability/Reactivity : The more stable the product, the more favorable its formation will be. In

terms of rates, this means that the more stable the product, the faster the reaction. (The concept here is

that the more stable the product, the more favorable it will be to make that product.)

Key note: Often the “product” that’s relevant in this context will not be the final product of the

reaction, but will be the “product” of the rate determining step.

Acidity

Why: Because as the stability of the anion products increases from A to D, the reactivity of the

parent acids increase

Reactivity of alkanes toward radical halogenation

Why: Because as the stability of the radical produced during the rate-determining-step increases,

the reactivity of the parent alkane increases

S N

1, E1 Reactivity

Why: Because as the stability of the cation produced in the rate-determining step increases, the

reactivity of the parent halide increases as well

3. Transition-State Stability/Reactivity : The more stable the transition state, the faster the reaction will

be. (The concept here is that the lower the transition state, the more easily it will be crossed.)

S N

2 Reactivity

Why: The pattern reflects the relative stability of the transition states. In the case of 3˚ versus 2˚ versus 1˚,

the issue is steric congestion in the transition state. The transition states for the more highly substituted halides are

destabilized. In the case of allylic halides, the transition state is stabilized for orbital reasons, not steric reasons.

CH

3

NH

2 OH

OH

O

CH

2

Na NHNa ONa ONa

O

A

B

C

D

H

3

C

CH

3 < <

3 ° plus resonance

Br

3 ° plus resonance

Br

1° plus allylic

Organic Chemistry II Review Jasperse Alcohol Syntheses 2

2 - Carbon

chain

extension

Mech

9 Mech

10 Mech

11 NaBH

4

will

not react with

esters

Mech

Review Routes to Alcohols

R'MgBr

2. H

3

O

ethylene

oxide

R'

OH

1 º alcohol

H H

R'MgBr

2. H

3

O

R'

OH

1 º alcohol

H H

R H

O

R

OH

H

1 º alcohol

LiAlH 4

2. H

3

O

aldehyde

H

NaBH 4

CH

3

OH

or

R R"

O

ketone

R

OH

R"

2 º alcohol

LiAlH 4

2. H

3

O

H

NaBH 4

CH

3

OH

or

R OR

O

R

OH

H

1 º alcohol

ester

H

LiAlH 4

2. H

3

O

R

OH

R

H

2

O, H

Markovnikov

R

OH

R

Markovnikov

Hg(OAc) 2

, H

2

O

NaBH 4

R

OH

R anti-Markovnikov

1. BH

3

- THF

2. H

2

O

2

, NaOH

R X R OH

S

N

2 mech, needs 1 º or 2 º system

and an excellent leaving group

NaOH

Organic Chemistry II Review Jasperse Alcohol Syntheses 3

Summary of Mechanisms, Ch. 10

For Test:

R Br + Mg

R + Br + Mg

R• + Br + Mg

Not for Test

R R'

O

1. Z

2. H

3

O

R R'

OH

Z

aldehyde

or ketone

or formaldehyde

Z may be R (RMgBr)

or H (NaBH 4

or LiAlH 4

R R'

O

Z

R R'

O

Z

H

3

O

R R'

OH

Z

mech:

R OR'

O

1. Z

2. H

3

O

R Z

OH

Z

esters

or

acid chlorides

Z may be R (RMgBr)

or H (LiAlH 4 )

R OR'

O

Z

R Z

O

OR'

mech:

Cl

+ HOR'

R Z

O

Z

R Z

O

Z

H

3

O

R Z

OH

Z

O

1. R

2. H

3

O

mech:

R

OH

O

R

O

H

3

O

R

OH

R

Organic Chemistry II Review Jasperse Alcohol Syntheses 5

10.8 Organometallics: RM (M = Metal) = R M

Li is analogous for making RLi,

which also act analogously.

MgBr is spectator: R is key.

1. Key: This is the way to make R , strong nucleophiles/bases

2. View as carbanions: RMgBr = R Super Strong Bases and Nucleophiles

The counterion metal is a spectator
Stability-reactivity principle: very unstable à very reactive
This great reactivity is very useful (as nucleophile)

3. Solvent and handling:

No water, alcohol, amines or acids allowed, or carbanion will just deprotonate them

o R + H

2

O à R-H + HO Destroys carbanion

If any chemicals with carbonyls are present, they too will react with the carbanion by

nucleophile/electrophile reaction

o

4. Two perspectives for dealing with organometallics in general and RMgBr in particular

Mechanistic Thinking: R
Predict-the-product thinking: R-MgBr: easier to see source and substitution product.

10.9 Addition of RMgBr to Carbonyl Compounds: Alcohols are Produced

Exothermic Addition of Carbon or Hydrogen Anions:

σ bond (made) stronger than π bond (broken)
oxygen anion more stable than carbanion

Carbonyl is strongly electrophile

much stronger even than a 1º alkyl iodide!

1. Breakable π bond

2. Carbonyl polarity

R Br RMgBr

Mg

R Br RLi + LiBr

2 Li

"Grignard Reagent"

O

R

O

R

R Br R MgBr

Mg Electrophile

R Electrophile

O

R'

O

R'

O

δ+

δ−

Organic Chemistry II Review Jasperse Alcohol Syntheses 6

Reaction Mechanisms for Grignard Reactions

Formaldehyde, Aldehyde, or Ketone as Carbonyl Compound (Reactions 4, 5, and 6)

1. Two simple steps:

a. Addition

b. Protonation

2. RMgBr = R-MgBr = R carbanion

a. The MgBr stuff is spectator, doesn’t need to be drawn in

Esters or Acid Chlorides: More Complex, Needs to Explain Two Additions and More Bond

Breakings

1. Four Step Mechanism:

a. Addition

b. Elimination

c. Addition

d. Protonation

Why? Kinetics and Reactivity. MEMORIZE.

R R"

O

1. R'

2. H

3

O

R R"

OH

R'

aldehyde

or ketone

or formaldehyde

R R"

O

R R"

O

R'

H

3

O

R R"

OH

R'

mech: R'

R OR"

O

R R'

OH

R'

acid chlorides

R OR"

O

R OR"

O

R'

mech:

+ HOR"

R R'

O

R R'

O

R'

H

3

O

R R'

OH

R'

1. R'

2. H

3

O

R Cl

O

esters or

acid chlorides

R'

Addition Elimination

Addition

Protonation

SLOW

fast

O

R H

O

R R

O

R OR

Aldehyde Ketone Ester

Steric Advantage.

Transition-state less

crowded and more stable

Stablized for electronic reasons

Therefore less reactive

Relative

Reactivity:

H 2

O

or

ROH

Acid/Base

Organic Chemistry II Review Jasperse Alcohol Syntheses 8

Mechanism

Aldehydes and Ketones

Esters

Cyclic Esters

Notes:

Mechanisms are exactly like with Grignard reactions
LiAlH 4

and NaBH

4

function as hydride anions H

LiAlH

4

is much stronger, NaBH

4

much weaker

1. Selective reduction : if both an ester and an aldehyde/ketone are present:

LiAlH 4

reduces both

NaBH 4

selectively reduces the aldehyde/ketone but leaves the ester untouched

2. LiAlH

4

is strong enough to react with and be destroyed by water or alcohol; NaBH

4

isn’t

LiAlH

4

+ H

2

O à H

2

(gas) + LiOH + AlH

3

+ heat

3. LiAlH

4

is strong enough to react with esters, NaBH

4

isn’t

R R"

O

R R"

OH

H

aldehyde

or ketone

or formaldehyde

R R"

O

R R"

O

H

3

O

R R"

OH

H

mech: H

or

H OCH

3

LiAlH 4

2. H

3

O

NaBH 4

CH

3

OH

or

NaBH 4

= H

LiAlH 4

= H

R OR"

O

R OR"

O

H

R H

O

H

Addition Elimination

SLOW

fast

R H

O

H

3

O

R H

OH

H

Addition

Fast

ester

+ OR"

H

O

H

Addition

Elimination

H

O

H

H 3

O

H

O

H

OH

H

OH H 3

O

Double Protonation

H

Add

NaBH 4

= B H

H

B

H

Na + H LiAlH 4

= Al H

H

Al

H

H

Na

Organic Chemistry II Review Jasperse. Alcohol Reactions 1

Summary of Alcohol Reactions, Ch. 11.

Deprotonation by a base.
Controlled by relative stability of RO

versus Z.

Consider relative electronegativity and

whether either anion is resonance

stabilized.

Potassium (K) analogous.
Key way to convert alcohol to

alkoxide, reactive as S

N

2 nucleophile

and E2 base.

Alkoxide formation-S N

2 route to ether

The electrophile R'-X must be S N

reactive, preferably 1º with a good

leaving group

Key access to aldehydes, which are

useful for more Grignard chemistry.

Note difference between PCC and

H

2

CrO

4

PCC does not react with 2º alcohols

very rapidly

Key access to ketones.
PCC does not react very fast with 2º

alcohols

Note difference between
PCC and H 2

CrO

4

when reacting with

1º alcohols.

HI, HCl analogous
Converts alcohol into a bromide that

can be used in Grignards, E2 reactions

Cation mechanism
Usually not method of choice for 1º, 2º

alcohols

R OH R ONa

Acid-Base

+ HZ

NaZ

R OH

R ONa

Na

R OH

R O R'

Na

2. R'-X

R H

O

Aldehydes

1 º Alcohols Only

PCC

OH

H

R R

O

OH

H

2

CrO 4

= Na 2

Cr 2

O

7

, H

2

SO

4

or CrO 3

/H

2

O

Ketones

2 º Alcohols Only

H

2

CrO 4

H

R OH

O

1 º Alcohols Only Acids

H

2

CrO 4

R H

OH

H

R H

R OH

O

Acids Aldehydes

H

2

CrO 4

R OH

R Br

Mech: Be able to draw!

3 º alcohols

HBr

Organic Chemistry II Review Jasperse. Alcohol Reactions 3

Mechanisms for ROH à RBr Reactions

Ch. 11 Reactions of Alcohols

A. Conversion to Alkoxides. Acidity of Alcohols and Phenols (10.6)

“alkoxide” = RO anion

1. Deprotonation by a base.

2. Controlled by relative stability of RO

versus Z.

3. Consider relative electronegativity and

whether either anion is resonance

stabilized.

Alcohols are weak acids à can be ionized by stronger bases
goes to the right (alkoxide) only if resulting RO is more stable than B
ex. NH 2

, CH

3

(nitrogen or carbon anions)

HBr

3 º mostly, sometimes 1 º

HBr Mech for 3 º ROH:

R OH

H Br

R OH

2

Br

Br

R-OH

R-Br

+ H

2

O

R

HBr Mech for 1 º ROH: R OH

H Br

R OH

2

Br

R-Br + H 2

O

PBr 3

Mech: R OH

R O

Br

PBr 2

H

PBr 2

Br

Br R

HO-PBr 2

R-OH

R-Br

R OH R ONa

Acid-Base

+ HZ

NaZ

Organic Chemistry II Review Jasperse. Alcohol Reactions 4

Acidity Table

Class Structure Ka

Acid

Strength Anion

Base

Strength

Base

Stability

Strong Acids H-Cl 10

2

Cl

Carboxylic Acid

5

Phenol 10

10

Water H

2

O 10

16

HO

Alcohol ROH 10

18

RO

Amine (N-H) RNH

2

33

RNH

Alkane (C-H) RCH

3

50

RCH

2

Notes/skills:

1. Be able to rank acidity.

2. Memorize/understand neutral OH acidity ranking: RCO

2

H > H

2

O > ROH

Reason: resonance stabilization of the anion
Alkoxide is destabilized relative to hydroxide by electron donor alkyl group

3. Predict deprotonation (acid/base) reactions

Any weak acid will be deprotonated by a stronger base (lower on table)
Any weak acid will not be deprotonated by a weaker base (higher on table)

4. Predict ether/water extraction problems

If an organic chemical is neutral and stays neutral, it will stay in ether layer
If an organic chemical is ionized (by an acid-base reaction), it will extract into the aqueous

layer

Key: a proton transfer will happen only if it results in a more stabilized anion

Key anion stability factors :

Electronegativity (oxygen > nitrogen > carbon)
Resonance. Carboxylate, phenoxide yes > hydroxide, alkoxide no
Donor/withdrawer factor: hydroxide > alkoxide (electron donor destabilizes anion)

R OH

O

R O

O

OH

O

Organic Chemistry II Review Jasperse. Alcohol Reactions 6

General Recognition of Oxidation/Reduction in Organic Chemistry

11.3, 11.4 Other methods for Oxidizing Alcohols. (No test)

There are lots of other recipes used for oxidizing alcohols (and for other oxidation reactions)

1. KMnO

4

2. CuO

3. “Jones”: H

2

CrO

4

with acetone added to temper reactivity

4. Collins: H

2

CrO

4

with pyridine added to temper reactivity

5. “Swern”: (COCl)

2

and (CH

3

2

S=O then NEt

3

In General: Recognizing Oxidizing versus Reducing Agents

Oxidizing Agents : Often have:

Highly Oxidized Metals or Nonmetals
Extra Oxygen

Reducing Agents : Often involve:

Hydrides in Formulas
Highly Reduced Metals
Metals + H 2
Metals + acid

OsO

4

KMnO

4

CrO

4

H

2

CrO

4

HNO

4

H

2

O

2

à H

2

O

RCO

3

H à RCO

2

H

O

3

à O

2

LiAlH

4

NaBH

4

Li, Na, K, Mg, Zn, Al, etc.

Pd/H

2

, Pt/H

2

, Ni/H

2

etc.

Zn/HCl, Fe/HCl, Zn/Hg/HCl, etc..

The ability to qualitatively recognize when a transformation involves an oxidation or reduction can

be very helpful.

The ability to recognize a reactant as an oxidizing agent or a reducing agent can be very helpful
Often on standardized tests!

C O

R

H

R

2 º alcohol

R H

O

Aldehyde

R OH

O

Carboxylic

Acid

R R

O

Ketone

or

H

C O

H

R

1 º alcohol

H

or

oxidation

reduction

oxidation

reduction

Oxidation : The number of oxygen bonds to a carbon increases,

and the number of hydrogens bonded to a carbon decreases

Reduction : The number of oxygen bonds to a carbon is reduced,

and the number of hydrogens bonded to a carbon increases.

More General : # of bonds to heteroatoms versus to hydrogens

Organic Chemistry II Review Jasperse. Alcohol Reactions 7

11.7- 9 Conversion of Alcohols to Alkyl Halides

HI, HCl analogous
Converts alcohol into a bromide that

can be used in Grignards, E2 reactions

Cation mechanism
Usually not method of choice for 1º, 2º

alcohols

Converts alcohol into a bromide that

can be used in Grignards, E2, S

N

reactions

Inversion of stereochem
Not good for 3º alcohols

Quick 2-step conversion of alcohol

into a nucleophilic Grignard

Retention of stereo!
Section 11- 9

Summary:

Class R-Br R-Cl

1º ROH PBr

3

SOCl

2

2º ROH PBr

3

SOCl

2

3º ROH HBr HCl

Vinyl or Aryl Nothing works Nothing works

Mechanism for H-X reactions with 3º Alcohols: Cationic (Test Responsible)

Notes:

1. Memorize the 3º alcohol mechanism (test responsible)

a. Protonate

b. Leave to give Cation. This is the slow step for 3º alcohols

c. Capture

2. Analogous with HI or HCl

3. S

N

1 type: carbocation-forming step is the rate-determining step, so R+ stability key

3º alcohols fastest
2º alcohols are way slower
1º alcohols (or vinyl/aryl) can’t react at all via this mechanism, because 1º R+ are too unstable.

4. HBr can also react with 1º ROH to give 1º RBr, although it is not often the method of choice

The mechanism is different, but rather interesting (not test responsible)

R OH

R Br

Mech: Be able to draw!

3 º alcohols

HBr

R OH

R Br

1 º or 2 º alcohols

PBr 3

R OH

PBr 3

or HBr

Mg

RMgBr

R OH

R Cl

1 º or 2 º alcohols

SOCl 2

HBr Mech for 3 º ROH:

R OH

H Br

R OH

2

Br

Br

R-Br

+ H

2

O

R

HBr Mech for 1 º ROH:

R OH

H Br

R OH

2

Br R-Br + H 2

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Organic Chemistry II Review Jasperse Basic Mechanism Principles 1

Reaction Mechanisms (see p. 310)

A. Recognizing/Classifying as Radical, Cationic, or Anionic

1. Radical

§ initiation requires both energy (either hv or Δ) and a weak, breakable heteroatom-heteroatom

bond

o Cl-Cl, Br-Br, O-O (peroxide), N-Br, etc..

2 Guides for That are Usually Reliable:

hv à radical mechanism

peroxides à radical mechanism

2. Anionic

§ a strong anion/base appears in the recipe

§ no strong acids should appear in the recipe

§ mechanisms should involve anionic intermediates and reactants, not strongly cationic ones

§ The first step in the mechanism will involve the strong anion/base that appears in the recipe

3. Cationic

§ a strong acid/electrophile appears in the recipe

§ no strong anion/base should appear in the recipe

§ mechanisms should involve cationic intermediates and reactants, not strongly anionic ones

§ The first step in the mechanism will involve the acid that appears in the recipe. The last step

will often involve a deprotonation step. Often the main step occurs in between the proton-

on and proton-off steps

B. Miscellaneous Mechanism Tips

1. Keep track of hydrogens on reacting carbons

2. Each step in a mechanism must balance

3. The types of intermediates involved (cation, anion, or radical) should be consistent with

the reaction classification above

a. If the reaction is cationic, don’t show anionic intermediates

b. If the reaction is anionic, don’t show cationic intermediates

4. Usually conditions are ionic.

5. Use a reactive species, whether strong anion or an acid, to start the first step

a. If acidic, first step will involve protonation of the organic

b. If anionic, the first step will involve the anion attacking the organic.

6. While it isn’t always easy to figure out what is a good mechanism, you should often be

able to eliminate an unreasonable mechanism.

Organic Chemistry II Review Jasperse Basic Mechanism Principles 2

Some Arrow-Pushing Guidelines (Section 1.14)

1. Arrows follow electron movement.

2. Some rules for the appearance of arrows

a. An atom (which must have a lone pair to give)

b. A bond pair (an old bond that breaks)

always go to some new atom.

3. Ignore any Spectator Atoms. Any metal atom is always a “spectator”

negative charge

4. Draw all H’s on any Atom Whose Bonding Changes

5. Draw all lone-pairs on any Atom whose bonding changes

6. KEY ON BOND CHANGES. Any two-electron bond that changes (either made or

broken) must have an arrow to illustrate:

7. Watch for Formal Charges and Changes in Formal Charge

must emanate from that atom or one of it’s associated bonds. There are two “more

positive” transactions:

atom. The atom has donated a lone pair which becomes a bond pair.

bond pair, so the arrow should emanate from the bond rather than from the atom.

point to that atom. Ordinarily the arrow will have started from a bond and will point to

the atom.

8. When bonds change, but Formal Charge Doesn’t Change, A “Substitution” is Involved

“substitution”.

formation of the new bond), and an outgoing arrow emanating from the old bond that

breaks

Organic Chemistry II Review Jasperse Some Fundamental Stability/Reactivity Principles 2

Stability/Reactivity/Selectivity Principles

1. Reactant Stability/Reactivity : The more stable the reactant, the less reactive it will be. In

terms of rates, this means that the more stable the reactant, the slower it will react. (The concept

here is that the more stable the reactant, the more content it is to stay as is, and the less

motivated it is to react and change into something different)

Key note: Often the “reactant” that’s relevant in this context will not be the original

reactant of the reaction, but will be the “reactant” involved in the rate determining step.

Why: As anion stability increases from A to D, the reactivity decreases

Why: As anion stability increases from A to D, the reactivity decreases

Why: As anion stability increases from A to D, the reactivity decreases

F

> Cl

> Br

> I

because F• > Cl• > Br• > I•

Why: Chlorine is more reactive the bromine because chlorine radical is less