Orgo II Exam 2

IMPORTANT things to remember for MC exam

\-For select all that apply questions, make sure you look at every option carefully. (If ==**charge**== is correct, if arrows are going the correct direction, configurations)

common electrophile

carbonyl

how to calculate oxidation state fast

Pick an atom that changes

If its connected to an atom more electronegative than +1

If its connected to an atom less electronegative than -1

(count double bonds twice)

add it all up: if oxid # went up, then it was oxidized

Electrophilic aromatic substitution

Benzene is nucleophile

general name of this structure

benzenium ion/cyclohexadienyl cation/ wheland intermediate

Rate determining step is

formation of benzenium

Nitration of benzene

benzene + HNO3 and H2SO4 → nitrobenzene

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electrophile is NO2+

Sulfonation of benzene

benzene + H2SO4 →

electrophile is SO3

Halogenation of benzene

benzene + Fe + Br2

electrophile is Bromine-Iron (III) Bromide complex

Friedel Crafts Alkylation

benzene + secondary halide or tertiary halide

electrophile is carbocation

==note:== subject to rearrangement

alkenes, which are converted to carbocations by protonation can be used to alkylate benzene

Freidel’s Crafts of Acylation

electrophile is acyl cation

==Do not rearrange==

Preparation of acyl chlorides

Freidel’s Crafts Acylation using anhydrides

no issue of rearrangement

Acylation-reduction

no issue of rearrangement

Substituent effect

\-To make a stronger nucleophile, put more electron density

\-To make weaker nucleophile, add more electronegativity

Electron Drawing Group (activating)

Ortho-Para Director

Electron Withdrawing group (deactivating)

Meta Director

examples: -CF3, -NO2, -SO3H, electropositive carbon

Halogens are…

deactivating but Ortho/Para directing

If multiple substituents,

Stronger EDG will dictate regiostreochemistry

EDG ranks highest to lowest

R2N-

RO-

R-

Cl,Br

Nucleophilic aromatic Substitution

Nucleophilic substitution

ortho and para sites of EWG react way faster

Tip for retrosynthesis

"An aromatic ring more deactivated than a monohalobenzene cannot be alkylated or acylated under Friedel–Crafts conditions."

organometallic nomenclature

attached alkyl group is prefix, metal is the parent

when metal bears two substituents, treat it as it was a anion

Grignard reagents

organomagneisum compounds

RX + 2Li with diethyl ether

RLi + LiX

RX + Mg with diethyl ether

RMgX

Reaction of organic halide with metal is ox-redox reaction

metal is oxidized/ reducing agent

synthesis of acetylenic alcohols

use terminal alkynes

orgozinc reagents for epoxides

ICH2ZnI is electrophile (due to empty p orbital)

Lithium dialkylcuprate (Gilman reagent)

P-toluenesulfonates

displaces halide as well, same sterochemistry

alkene to alcohol (OH to most substituted)

Use H2SO4 and H2O

alkene to alcohol (OH to least substituted)

1\.B2H6, diglyme


2. H2O2, OH-

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3 ways for reduction

First way: NaBH4 and methanol/H2O/ethanol

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Second way:


1. LiAlH4, diethyl ether
2. H2O

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Third way:

H2, Pt, ethanol

LiAl4 and NaBH4 are

nucleophiles/reducing agents

reduction of carboxylic acid

turns to primary alcohol (turns to aldehyde first)

Diol nomenclature

alkane + #,# diol

dihydrooxylation of alkene

conversion of alcohols to ethers

Esterfication

retention of configuration

Primary alcohol to carboxylic acid

use K2Cr2O7 and H2SO4, and H2O

Primary alcohol to aldehyde

PCC and CH2Cl2

Secondary alcohol to ketone

First way: Na2Cr2O7, H2O and H2SO4

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Second way: PCC, CH2Cl2

oxidizing tertiary alcohols

Tertiary alcohols are NOT readily oxidized → No reaction

Swern Oxidation

oxidative cleavage of vicinal diols

thiol nomenclature

similar to diol, it OH group present, then use prefix sulfonyl- or mercapto-

thiols are

strong smelling (skunk fluid)

alkyl halide with -SH

change of configuration

Disulfide formation

Ether nomenclature

list the two alkyl groups and add ether at the end

ether oxygen is a hydrogen bond acceptor

which means soluble in water

Crown nomenclature

Total # of atoms-crown-# of oxygens

18-crown-6 solubilizes

potassium salts

Ethers from alcohol and alkene

1. protonation
2. add O group
3. deprotonation

make vicinal halohydrins from alkene

trans addition

vicinal halohydrins to epoxide

Use NaOH and H2O

Williamson ether synthesis

ONLY primary halides,

secondary halides undergo E2

preparing sulfides

change of configuration

acid catalyzed cleavage of bonds

formaldehyde

PCC

PDC

acyl chloride in ester formation mechanism

dehydrobromination

use base for secondary and tertiary bromides

anhydride ester formation

ethylene oxide

hint: if you see two carbons added on, (LLOK AT QUIZ

most electronegative atoms

F, O, N, Cl

condensation

two molecules come to form one larger one and some smaller molecule

previous alcohol reactions table in ch 16

use of NBS

allyl vs vinyl

sp2 carbons

SN2 reactions cannot occur with leaving groups (X) bonded to sp2-hybridized carbons

17\.8

primary alcohol using a Grignard reagent

Use Formaldehyde

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As with carboxylic acids, esters may be reduced using lithium aluminum hydride to give primary alcohols

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Bromobenzene into 2-phenylethanol

If you see two added carbons to make a primary alcohol hints to

1\.ethlyene oxide

2\. H3O+

hydroboration-oxidation

syn addition, OH to least substituted

primary alcohol to carboxylic acid use

use HCrO4

or Na2Cr2 O7 in sulfuric acid

primary alcohol to aldehyde

PCC (or PDC) and CH2Cl2

hydroboration-oxidation of 1-phenylcyclobutene

alkyne to alkane

alkyne to trans alkene

alkyne to cis alkene

For addition, usually makes the most stable carbocation.

hydrolysis

ozonolysis

ozonolysis intramolecular

NMR of alcohol

The broad band in the IR spectrum at 3300 cm-1 is the O—H stretching vibration of an alcohol. The presence of an alcohol is confirmed by the disappearance of a peak following addition of D2O as the hydroxyl proton undergoes rapid exchange with deuterium. "

stereochemistry of Williamson ether synthesis

the ether product has the same absolute configuration as the starting alkoxide because no bonds to the chirality center are made or broken in the reaction

vicinal halohydrins with base

turn into epoxides (intramolecular Williamson ether synthesis)