U of S CHEM250 - Organic Chemistry Final Notes

09/04/08 10:09:19 PMMidterm Notes

1

I. Chapter 1A. ElectronegativityB. HybridizationC. Functional groupsD. PriorityE. Resonance

II. Acids & BasesA. ArrheniusB. Bronsted-Lowry

1. pKaa) structure

(1) resonance(2) inductive effect

b) rankingC. Lewis

III. CycloalkanesA. Neuman projectionsB. Cyclohexane

1. chair/boat conformations2. axial/equatorial positions

a) equatorial monosubstituted most stable

IV. Alkenes & AlkynesA. Cis/trans isomerismB. E/Z isomerism

V. Reactions of AlkenesA. Hydration

1. ALKE + H2O —[H+]—> ALKY–OH2. Markonikoff's rule

B. Halogenation1. ALKE + Br2 or Cl2 —> Br–ALKY–Br2. trans-diaxial addition

a) no cis isomerb) 2 entantionomers

C. Hydrohalogenation1. ALKE + HX (X=halogen) —> ALKY—X

D. Hydrogenation (Reduction)1. ALKE + H2 —Ni, Pd, Pt—> ALKY

E. Energy Diagrams1. ΔH —> energy difference between products and reactants

VI. StereochemistryA. Constitutional IsomersB. Stereoisomers

1. diasteriomersa) trans/cisb) non-mirror images

2. entantiomersa) non-superimposable mirror images

3. meso compoundsa) not isomersb) has plane of symetryc) can be rotated to form original compound

VII. HaloalkanesA. SN1 vs SN2

1. SN1a) 2 step processb) formation of carbocationc) at stereocentres

(1) racemic mixture of products(2) random attack

2. SN2a) 1 stepb) formation of intermediatec) at sterocentres

(1) backside attack(2) inversion of configuration

B. E1 vs E2 — ß- Elimination1. Zaitsev's Rule

a) major product will be most substituted at double bond2. E1

a) 2 stepb) formation of carbocation

(1) protic solvents3. E2

a) Concerted process(1) 2° & 3° haloalkanes

VIII. Alcohols, Ethers & ThiolsA. Alcohol reactions


2

VIII. Alcohols, Ethers & ThiolsA. Alcohol reactions

1. ROH + Ca/Na/K2. ROH + HX —> R–X + HOH3. ROH —H2SO4 or H3PO4—>4. ROH —PCC—> R=O H carbonyl group

B. Ethers1. Epoxide formation

a) in cyclic compounds(1) cis product

2. Epoxide reactionsa) trans product

IX. Benzene and DerivativesA. Resonance energy

1. difference in energy between resonant structure and its most stable contributing structure without resonanceB. [D1]Aromaticity (Huckel's rule)

1. Must be cyclic

a)

2. Must be planar3. each atom of the ring must have a p orbital perpendicular to the plane of ring

a)

4. must contain 4n+2 pi electrons

a)

C. [D2]Heterocyclic Aromatics1. Heterocyclic compound

a) compound that contains one or more atoms other than carbon in its ring

b)

2. Heterocyclic aromatic compound


3

IX. Benzene and Derivatives

C. [D2]Heterocyclic Aromatics1. Heterocyclic compound

b)

2. Heterocyclic aromatic compounda) heterocyclic compound whose ring is aromatic

b)

D. Nomenclature1. Phenyl group (Ph-)2. Disubstituted benzenes

a) ortho (1,2)b) meta (1,3)c) para (1,4)

3. Polysubstituted benzenesa) number atoms of ringb) if a group imparts special name, use as parent

(1) eg. phenol, toluenec) otherwise number to give smallest numbers and list alphabetically

E. [D2,D3,D4]Reactions of benzene1. characteristic reaction of aromatic compounds is Electrophilic Aromatic Substitution

a) General Mechanism:

(1)

2. Nitrationa) substitution with nitro group NO2

b)

3. Friedel-Crafts Alkylationa) forms C-C bond with an alkyl groupb) Arene + alkyl halide —AlCl3—> Arene-alkyl + H-halide

(1)

(2)


4


E. [D2,D3,D4]Reactions of benzene

3. Friedel-Crafts Alkylation

b) Arene + alkyl halide —AlCl3—> Arene-alkyl + H-halide

(1)

(2)

c) practical only with stable carbocations as electrophiles (2° & 3°)d) fails if benze ring bears electron-withdrawing group

(1) double or triple bond(2) alkyl halides(3) nitro(4) 4° amines

4. Friedel-Crafts Acylationa) Arene + Acyl halide —AlCl3—> Arene-acyl (ketone) + H-halide

(1)

5. Sulfonation:a) Arene + Sulfuric acid —> Arene-SO3H + H2O

6. Other Benzene Alkylations

a)

F. Di and polysubstitution1. pre-existing groups influence further substitution in rate and orientation2. orientation

a) ortho-para directors(1) lone pairs

b) meta directors(1) no lone pairs

3. Ratea) activating

(1) electron donating groupsb) deactivating

(1) electron withdrawing groups4. Ortho-Para directors — all activating except for halogens — all have lone pair of electrons

a) strongly activating(1) amines(2) hydroxyl(3) alkoxy

b) moderately activating


5


F. Di and polysubstitution

4. Ortho-Para directors — all activating except for halogens — all have lone pair of electronsa) strongly activating

(3) alkoxyb) moderately activating

(1) NHCOR(2) OCOR

c) weakly activating(1) aryl(2) alkyl

d) weakly deactivating(1) halogens

5. Meta-directors — all carry full or partial positive charge where bonded to ringa) moderately deactivating

(1) aldehyde(2) ketone(3) carboxylic acid(4) ester(5) amide(6) SO3H

b) strongly deactivating(1) NO2(2) NH3+(3) CF3(4) CCl3

6. Rate-determining step usually formation of cation intermediateG. Phenols

1. Phenols greatly more acidic than alcoholsa) greater stability of phenoxide ionb) ring substituents, particularly X and NO2, increase acidity

X. AminesA. Structure & Classification

1. 1°,2°,3°a) N atom is bonded to 1, 2 or 3 groups

2. 4°a) N atom is bonded to 4 groups and bears a positive charge (no lone pair)

3. Aliphatica) N bonded only to alkyl groups

4. Aromatica) N bonded directly to one or more aryl group

5. Heterocyclica) amine in which nitrogen is one of the atoms of a ring

B. [D4,D5]Nomenclature1. Aliphatic 1°

a)

2. 2° & 3°

a)

3. Aromatica) aniline is parent

b)


6

X. Amines

B. [D4,D5]Nomenclature

3. Aromatica) aniline is parent

b)

4. Amine has very low priority

a)

(1) should be 2-aminobenzoic acidC. Basicity

1. all amines are weak bases2. aromatic amines weaker bases than aliphatic

a) no resonance stabilization once protonated(1) benzene aromatic ring interrupted

3. electron-withdrawing groups decrease basicity by decreasing availability of lone pair on nitrogenD. Reaction with Acids

1. amines form water-soluble salts in strong acids

XI. Aldehydes and KetonesA. [D5]Structure

1. Aldehyde group

a)

2. Ketone Group

a)

B. [D5]Nomenclature1. Aldehydes

a) parent is longest chain including the carbonyl group(1) suffix is -al

(2)

b) cyclic molecules(1) suffix is -carbaldehyde

(2)


7

XI. Aldehydes and Ketones

B. [D5]Nomenclature1. Aldehydes

b) cyclic molecules(1) suffix is -carbaldehyde

(2)

2. Ketonesa) linear or cyclic

(1) suffix is -one

(2)

3. If priority is lower than other functional groups, then use prefix oxo-

a)

C. Physical Properties1. polar compounds with dipole-dipole interactions2. higher boiling point and more soluble than non-polar compounds

D. [D6,D7,D8,D9]Reactions1. Grignard reacents

a) carbon nucleophiles with formula R-Mg-Xb) carbanion adds to the carbonyl group of aldehydes and ketonesc) Grignard reactants are very strong bases

(1) react with protic acids to form alkanesi) CH3-CH2-MgBr + H(+) —> CH3-CH2-H + Mg(2+) + Br(-)

(2) any compound with OH, NH, or SH bond reacts with a grignard reagent by proton transfer

i)

ii) Wateriii) Alcoholsiv) Phenolsv) Carboxylic Acids

vi) Aminesvii) thiols

d) Reaction with methanal (formaldehyde) gives 1° alcohol

(1)


8


D. [D6,D7,D8,D9]Reactions1. Grignard reacents

d) Reaction with methanal (formaldehyde) gives 1° alcohol

(1)

e) reaction with other aldehydes gives 2° alcohol

(1)

f) reaction with ketones gives 3° alcohol

(1)

2. Hemiacetala) molecule with -OH and -OR bonded to same carbon

(1)

b) minor components of equilibrium unless cyclic

(1)

3. Acetala) molecule with 2 -OR groups bonded to same carbon

(1)


9


D. [D6,D7,D8,D9]Reactions

3. Acetala) molecule with 2 -OR groups bonded to same carbon

(1)

b) Examples

(1)

(2)


10



3. Acetal

b) Examples

(1)

(2)

4. Iminesa) molecule with a C=N bond, also schiff baseb) formed by reaction of an aldehyde or ketone with ammonia or 1° amine

(1)

5. Keto-Enol Tautomerisma) enol

(1) molecule containing an -OH group on a carbon-carbon double bond of an alkene(2) proportion of enol form generally insignificant

(3)

b) interconversion between tautomers catalyzed by both acids and bases(1) enantiomerically pure aldehydes and ketones slowly become racemic in acids or bases as the tautomers interconvert, since enols are achiral

(2)

6. α-Halogenationa) aldehydes and ketones with alpha hydrogen, react with Br2 and Cl2 to give an alpha haloaldehyde or ketoneb) intermediate is an enol

(1)

7. Metal Hydride Reductiona) aldehydes can be reduced to 1° alcoholsb) ketones reduced to 2° alcoholsc) common reagents NaBH4 and LiAlH4

d)


11



7. Metal Hydride Reduction

c) common reagents NaBH4 and LiAlH4

d)

XII. Carboxylic AcidsA. Structure

1. functional group is a carboxyl groupa) -COOH

b)

B. Nomenclature1. suffix -oic acid

a)

2. -dioic acid for dicarboxylic acids

a)

3. group has higher priority than most others4. cyclic carboxylic acids name cyclic chain and add suffix -carboxylic acid

a)

5. aromatic carboxylic acids

a)


12

XII. Carboxylic Acids

B. Nomenclature

5. aromatic carboxylic acids

a)

C. Physical Properties1. hydrogen bonding

a) significantly higher boiling pointsb) more soluble in water

2. weak acidsa) acidity greater than alcohols due to resonance stabilizationb) pKa 4–5c) electron withdrawing substituents near carboxyl group increase acidity due to inductive effects

D. Reactions1. Reaction with bases

a) carboxylic acids react with strong bases (NaOH, KOH), ammonia and amines to form water soluble saltsb) carboxylic acids react with NaHCO3 and NaCO3 to form water-soluble salts and carbonic acid (H2CO3) which breaks down to CO2 and H2O

2. Reductiona) carboxyl group very resistant to reduction

(1) not reduced by H2/metal catylist(2) not reduced by NaBH4

b) LiAlH4 reduces carboxyl group to a 1° alcohol

(1)

3. Fischer Esterificationa) Esters prepared by treating carboxylic acid with an alcohol with acid catylist

(1)

4. Acid Chloridesa) carbonyl group bonded to Clb) prepared by treating a carboxylic acid with thionyl chloride

(1)

5. Decarboxylationa) loss of CO2 from carboxyl groupb) most carboxylic acids if heated to very high temperature undergo thermal decarboxylationc) if carbonyl group beta to carboxyl group, mild heating only required

(1)


13

XII. Carboxylic Acids

D. Reactions

5. Decarboxylation

c) if carbonyl group beta to carboxyl group, mild heating only required

(1)

XIII. Functional Derivatives of Carboxylic AcidsA. Types

1. Acid Chloridesa) acyl group bonded to a halogenb) name with suffix -yl chloride

(1)

2. Acid Anhydridesa) two acyl groups bonded to an oxygen atomb) name by replacing acid of parent by anhydride

(1)

3. Estersa) acyl group bonded to -OR or -OArb) name by replacing -ic acid with -ate

(1)

4. Amidesa) acyl group bonded to a trivalent nitrogenb) name by replacing -ic acid with -amidec) if amide nitrogen bonded to alkyl or aryl group, name group using N as locator

(1)

B. Reactions1. Characteristic reaction: Nucleophilic acyl substitution


14

XIII. Functional Derivatives of Carboxylic Acids

B. Reactions1. Characteristic reaction: Nucleophilic acyl substitution

a) an substitution of one nucleophile for anotherb) forms tetrahedral intermediate like SN1 reactions

(1)

c) COR group staysd) Nucleophile

(1) weaker the lewis base, the better the leaving groupi) (best) X > COOR > OR > NR2

ii) (highest nucleophlic substitution reactivity) Acyl chloride > Acid anhydride > Ester > Amide2. Hydrolysis

a) Acid Chlorides(1) low molecular weight acid chlorides react rapidly with water; higher weight less reactive

(2)

b) Acid Anhydrides(1) low weight very reactive; higher weight, less reactive

(2)

c) Esters(1) hydrolysed very slowly unless with aqueous acid or base(2) Acid-catylized (catylitic ammounts)

i)

ii) reversible(3) Base-promoted (1 mole per mole ester)

i)

ii) irreversibled) Amides

(1) Both acid and base reactions require equimolar quantities(2) acid-promoted

i) products are carboxylic acid and ammonium or amine salt

ii)

(3) base-promotedi) products are carboxylate salt and an amine

ii)

3. Reaction with Alcoholsa) Acid chlorides react with alcohols to give an ester and HCl


15


B. Reactions

3. Reaction with Alcoholsa) Acid chlorides react with alcohols to give an ester and HCl

(1)

b) Acid Anhydrides react with alcohols to give an ester and a carboxylic acid

(1)

c) Esters undergo tranesterification(1) acid catalysed exchange of the OR group

(2)

d) Amides do not react with alcohols under any conditions4. Reaction with Ammonia and Amines

a) Acid halides(1) react with ammonia, 1° amines and 2° amines to form amides(2) not 3° amines: require free hydrogen(3) require 2 moles of amine: 1 to form amide, 1 to neutralize HCl

(4)

b) Acid anhydrides(1) react with ammonia, 1° amines and 2° amines to form amides(2) 2 moles required

(3)

c) Esters(1) react with ammonia, 1° amines and 2° amines to form amides

i) less reactive than either acid halides or anhydridesii) only 1 mole required

(2)

d) Amides do not react with Ammonia or Amines5. Esters with Grignard Reagents

a) an ester reacted with 2 moles of Grignard reagents gives a 3° alcohol (2° with methanoate)

(1)


16


B. Reactions

5. Esters with Grignard Reagentsa) an ester reacted with 2 moles of Grignard reagents gives a 3° alcohol (2° with methanoate)

(1)

6. Reduction of Estersa) unlike aldehydes and ketones, esters are only reduced by LiAlH4 to two alcohols

b)

7. Reduction of amidesa) LiAlH4 reduction of an amide gives 1°, 2°, or 3° amines

b)

U of S CHEM250 - Organic Chemistry Final Notes

Documents

Transcript of U of S CHEM250 - Organic Chemistry Final Notes