IIT JEE , AIEEE Forum - Chemistry , Organic Chemistry

goVniitian

Can any1 plz explain exactly how LiAlH^_4,_{^NaBH4 ^{and H}2^{/Ni and Lindlar's catalyst reduce substances differently?and to what extent?}}

_{^{-when there are double bonds+carbonyl groups?}}

_{^{-when they are in conjugation?}}

_{^{-in rings?(heterocyclic)}}

_{^{This is really basic but i'm confused!}}

sandeepramesh

they reduce by H- .

For unsaturated carbonyls (alpha beta) michael addn occurs

eistien

LiALH4 reduces all compounds and is more reactive than selective whereas NaBH4 is less reactive and reduces only C=O and not C=C!!!

uday_zingtudor

Functional group change	LaAlH4	NaBH4	B2H6	Metal/H2
Aldehyde to alcohol	Yes	Yes	Yes	Yes
Ketone to alcohol	yes	yes	Yes	yes
Acid to alcohol	yes	no	Yes	yes
Acid chloride to alcohol	yes	yes	no	yes
Ester to alcohol	yes	no	yes	yes
Acid anhydride to alcohol	yes	no	Yes	yes
Alkene to alkane	no	no	Yes	yes

hope u find this table useful

does anyone know how to prepare reaction charts on my sys???

Cheerio!!!

sweet08

LIALH---

carbonyl compds reduced without redn double/triple bonds.

note:sometimes =bond is redn if phenol is at beta carbon

acid der----alcohol

amides{unsubstituted}----------primary amines

subs---------------------2/3 amines

nitro,azides,oximes,nitriles,----------1 amines

halides--------------hydrocarbon

epoxide------------alcohol

NaBH4---

milder redn agent than lialh4

more selective

it reduces carbonyl groups of ald,keto,acid chlorides in presence of many reducible groups such as nitro, ester, carboxyl, epoxide, nitrile, double bond{either isolated/conjugated} are not affecte

suppose to red p-nitro benzaldehyde to p-nitro benzyl alcohol NaBH4 is used but not LIALH as it reduces both

this high selectivity makes NaBH4 preffered reagent for redn of carbonyl compds in sensitive polyfunctional molecules

H2/Ni

powerfl redn agent

it redcs multiple bonds in aliphatic&alicyclic&aromatic compds

aromatic ethers---------hydc

Ar0R------------------------>ArH+RH

nitro------------amino

nitriles----------------------ald/amines

plz rate me

ankitagg

in ^NaBH4 ,it reduces to H-.
^NaBH4

Na+ +BH3 +H-

in LiAlH_{4 ,} it too reduces to H- as
LiAlH_{4Li+ +AlH3 +H-

in H2/Ni Ni absorbs hydrogen at its surface and then the reactant attacks .

and at last lindler's catalyst acts at catalyst poison in the prepration of alkenes by hydrogenation of alkynes.}

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