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88 terms

Kaplan MCAT OChem Ch. 7: Alcohols and Esters

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alcohol
general formula is ROH
hydroxy group
OH
alcohol
water molecule loses a proton when it attaches to an alkyl grouop => restoring neutrality
alcohol
can be protic solvents
alcohol
OH has highest priority
alcohol naming
alkyl group + alcohol
phenol
alcohols attached be aromatic
phenol
ArOH
phenol
resonance of ring and lone pair of oxygen make H of alcohol more acidic that other alcohols
phys. prop. of alcohols
BP of alcohols higher than hydrocarbons, due to H bonding
phys. prop. of alcohols
more than one OH group => greater degree of H bonding
phys. prop. of alcohols
OH hydrogen weakly acidic
phys. prop. of alcohols
alcohols can dissociate into protons and alkoxy ions (like water does protons and hydroxide ions)
phys. prop. of phenols
OH hydrogen of this are more acidic => dist'n of neg charge throughout ring => stabilizing anion
phys. prop. of phenols
for intermolecular H bonds and relatively high MP and BP
phys. prop. of phenols
slight soluble in water as are some of its derivatives
phys. prop. of phenols
can form salts w/ inorganic bases such as NaOH
phys. prop. of phenols
presence of other sub affect acidity, BP, and MP of phenols
phys. prop. of phenols EWG
inc. acidity

along w/ resonance, it stabilizes the alkoxy anion => alcohol more acidic
phys. prop. of phenols EDG
dec acidity

as more alkyl groups (electron donating) attach -> destabilize alkoxide anion
phys. prop. of alcohol (aliphatic)
more alkyl groups => less acidic molecule
phys. prop. of alcohlols w/ carbocations
alkyl groups donate electron density => stabilize pos charge but destabilize neg. charge
Big Three Mechs for alcohol and ethers
1. Nu Su (Sn1 and 2)
-water to DB

2. Nu add to carbonyl

4. oxi-red (more oxygen bonded, more oxidized)
types of synthesis of alcohols
addition

substitution

reduction

phenol
addition synthesis of alcohol
prepared by adding organometallic compoundss to carbonyl groups
sub synthesis of alcohol
both sn1 and sn2 under proper conditions
reduction synthesis of alcohols
this of aldehydes, ketones, carb acids, or esters
reduction synthesis of alcohols
LAH or NaBH4 are two common this reagents
LAH
powerful reducing agent, just about anything
NaBH4
weaker than LAH, reduces aldehydes, ketones, or acyl chlorides, but CANNOT:

esters, carb acids, or amides
phenol synthesis of alcohols
maybe be from arylsulfonic acids w/ hot NaOH, however this is only useful only for phenol or its alkylated derivatives
phenol synthesis of alcohols
more versatile method is hydrolysis of diazonium salts
reducing agents
have a lot of Hs
oxidizing agents
have a lot of Os
alcohol rxns
elimination

substitution

oxidation
alcohol elimination
these can be dehydrated in strongly acidic solution (usually H2SO4) => alkene
alcohol elimination
mech of dehydration is E1 for secondary and tertiary these
alcohol elimination
mech of dehydration is E2 for primary these
alcohol elimination
OH group can be protonated and converted to a good LG
alcohol elimination
more stable alkene as major product

occurs via movement of proton (hydride shift)
alcohol elimination
milder method uses POCl3 (phos. oxychloride) => E2 mech for primary and secondary alcohols

OH as LG
alcohol sub rxn
OH group turns into water, a good LG for Sn1
alcohol sub rxn
this converted to tosylate (p-toluenesulfonate) group, making good LG for Sn2 reactions
alcohol sub rxn
convert this to alkyl halides, common is forming inorganic esters which undergo Sn2 reactions

alcohols + thionyl chloride => intermediate inorganic ester (chlorosulfite) and pyridine => Cl- backside carbon => SO2 and Cl-, making alkyl chloride w/ inversion of config
alcohol sub rxn
treated w/ PBr3 (pyridine) => alkyl bromide

OH turned into good LG
alcohol sub rxn
phenols undergo EAS since lone pair of O donate to ring -> OH strongly activating => ortho/para-directing
alcohol oxi-red rxn
generally involves some form of chromium (VI) as oxidizing agent => reduced to chromium (III)
alcohol oxi-red rxn (PCC)
only mild (anhydrous) oxidant
alcohol oxi-red rxn (PCC)
partially oxidizes primary alcohols => aldehyde => stops since lacks water to hydrate aldehyde (aldehydes easily hydrated)
alcohols become better LG by
1. protonation

2. convert to tosylate

3. form an inorganic ester
electron donating sub
when lone pair from oxygen
alcohol oxi-red rxn aldehyde
when hydrated (gem diols or 1,1-diols) => can be oxidized to carb acids
alcohol oxi-red rxn (PCC)
form ketones from 2ndary
alcohol oxi-red rxn (PCC)
3rd alcohols already oxidized as can be, so don't react w/ any of oxidizing agents
alcohol oxi-red rxn (alkali dichromate salt)
fully oxidze primary and secondary alcohols

1 - to carb acids
2 - to ketones
alcohol oxi-red rxn (CrO3)
even strong oxidant

often dissolved w/ dilute sulfuric acid in acetone
alcohol oxi-red rxn (CrO3)
reaction called Jone's oxidation
alcohol oxi-red rxn (CrO3)
oxidizes:

1 - carb acids
2 - ketones
phenol oxi-red rxn
w/ oxidizing reagents => produce quinones
ether
two alkyl (two aryl) bonded to an oxygen atom
ether
ROR
ether
important solvents, but are aprotic and unreactive
ether (naming)
alkyl alkyl ethers
ether (naming)
exception are cyclic ethers, as their aren't two diff. alkyl
ether (smaller rings)
more angle strain => less stable and more reactive
phys. prop. of ethers
don't H bond
phys. prop. of ethers
boil at low temp compared w/ alcohols, actually do at approx. same temp as alkanes of comparable MW
phys. prop. of ethers
only slightly polar => only slightly soluble in water
phys. prop. of ethers
inert to most organic reagents => freq. used as solvents
williamson ether synthesis
produce ether from rxn of metal alkoxides w/ primary alkyl halide or tosylates
williamson ether synthesis
alkoxides as Nu => displace halide or tosylate via Sn2 => ether

competes w/ E2
williamson ether synthesis
alkoxides w/ ONLY attack nonhindered halides
williamson ether synthesis of phenols
relatively mild rxn conditions, since acidity of these
williamson ether synthesis of phenols (cyclic ethers)
intramolecular rxns forced since rate and equilibrium of rxn affected by reagent conc.

reagents see fairly high conc. of each other
williamson ether synthesis of phenols (cyclic ethers)
oxidation of an alkene w/ a peroxy acid (gen. formula RCOOOH) like mcpba
reaction w/ ethers
peroxide formation

cleavage
peroxide formation
ethers react w/ oxygen => highly explosive peroxides
cleavage (straight-chain ethers)
under vigorous conditions, usually at high temp in presence HBr or HI
cleavage (straight-chain ethers)
initiated by protonation of ether oxygen
cleavage (straight-chain ethers)
can be sn1 or sn2, depending on conditions and structure of ether
cleavage (straight-chain ethers)
alcohols products usually react w/ second molecule of hydrogen halide => alkyl halide
SB
poor LG
cleavage (highly strained cyclic ethers)
epoxides ready to react and doe Sn2
cleavage (highly strained cyclic ethers)
catalyzed by acid treated or reacted w/ base (Nu)
cleavage (highly strained cyclic ethers)
symm. epoxides => either C can be Nu attacked
cleavage (highly strained cyclic ethers)
asymm. epoxides => most sub. C is Nu attack when catalyzed w/ acid; least sub C w/ Nu (basic conditions)
cleavage (highly strained cyclic ethers)
base (nu) this mostly Sn2 occurs at least hindered (least sub)

environment is basic, so better Nu than in acidic environment
cleavage (highly strained cyclic ethers)
acid-catalyzed is Sn1 and some Sn2

O is protonated => better LG

sub stabilizes charge, so more sub, good target for Nu attack