Reaction Reagents 8 Flashcards
alcohols have – BP?
much higher BP bc it can do HB with O or H
alcohols are
amphoteric! act as base or acid
making alkoxide reaction
alcohol gets deprotonated by strong acid (NaH) or becomes salt with metal (Na, K, Li)
H- of NaH acts as base and removes H from OH of alcohol making alkoxide
Factors that stabilize alcohols and phenols?
- resonance: phenol + benzene + OH
- induction: add EWG to OH
- solvation effects: less sterically hindered = can solvate and stabilize charge better = stronger acid
alcohol synthesis from alkyl halide
substitution:
primary alkyl halide + strong nuc/base -> alcohol (Sn2)
tertiary alkyl halide + weak base -> alcohol (Sn1)
alcohol synthesis from alkenes
addition rxns
ACID CATALYZED HYDRATION
alkene pi attacks H on H3O, makes carbocation, carbocation gets attacked by H2O, gets deprotonated (OH ends up on most subbed C)
HYDROBORATION OXIDATION
alkene attacks B on BH3, and BH2 adds to least hindered group, H2O2 + NaOH substitutes BH2 (OH ends up on least subbed C)
DIOLS
syn: OsO4/KMnO4
anti: peroxyacid - 1)RCO3H, 2)H3O+
How can you determine oxidation state of C?
treat bonds as ionic and count a neg charge to most EN atom in bond
What is the general mechanism of reduction to make alcohols?
carbonyl group has pi bond, C in pi bond gets attacked, other group adds to C and O on carbonyl gets protonated
catalytic hydrogenation reaction to make alcohol
carbonyl + H2 + metal catalyst (Pt, Pd, Ni)
adds H to C and O turns to OH, pi bond becomes single bond
this is not selective; all pi bonds get H’s added
carbonyl + NaBH4 (sodium borohydride)
H of BH4 attacks C of C=O -> puts H on to carbonyl C
O- of carbonyl intermediate attacks proton donor (H2O, EtOH, MeOH) to protonate O
makes alcohol
**
unsymmetrical ketone or aldehyde gets attacked by H- on either side = enantiomers**
NaBH4 is a common reducing agent for aldehydes and ketones
carbonyl + LiAlH4 (lithium aluminum hydride)
H of AlH4 acts as H-, adds C to C=O of carbonyl
second step: proton donor for O- to become OH
alcohol formation
How does NaBH4 compare to LAH?
LAH stronger bc Al is less EN than B so more polarized bond of H-Al
What can LAH reduce that NaBH4 can’t?
esters and carboxylic acids ==> makes primary alcohols
ester + LAH
- H of LAH attacks C of C=O
- single bonded O (and its group) (alkoxide) LG
- double bond C=O reforms
- H of LAH attacks C of C=O again
- O- from carbonyl basic attack on proton donor
makes primary alcohol
alkyl halide + Mg metal
R-Mg-X = C-
C- = really good nucleophile = strong base
can’t be made in presence of proton source
carbonyl + grignard
- grignard C- attacks C on C=O forming new C-C bond
- O- on carbonyl basic attack a proton source
makes alcohol
reacts with ester, aryl, aldehyde, or ketone
how can grignard react when the alkyl halide has an acidic H?
ex making a diol from an alcohol
- protect alcohol with trimethylsilyl (TMS-Cl) and Et3N
- removes acidic H and now have TMS (or OTMS if alcohol to start)
- react was Mg to make grignard C-
- react with carbonyl group
- protonate alkoxide of carbonyl group with water
- add fluoride (TBAF) to deprotect
alcohol + HCl + ZnCl2
- OH nuc attack on ZnCl2 (lewis acid)
- ZnCl2 makes OH better LG
- Cl- attacks C that was C-OH and OHZnCl2 leaves
- make alkyl chloride
alcohol + 1) TsCl + py +2? NaBr
- TsCl, py converts OH into OTs (good LG)
- Br- (or other halide) substitution rxn
- makes alkyl halide
1º or 2º alcohol + SOCl2, py
- O of OH attacks S on SOCl2, making good LG
- Cl- leaves and then attacks C- that has SO2Cl which leaves
- makes alkyl chlorine
chlorination of alcohol
1º or 2º alcohol + PBr3
- OH O attacks P, Br- leaves
- Br- attacks C that is attached to PBr2, OHPBr2 leaves
- alkyl bromide made
bromination
oxidation of 1º alcohol
aldehyde -> carboxylic acid
2º alcohol oxidation
ketone
3º alcohol oxidation
no rxn (no H on alpha C)
