addition reaction of carbonyl

8/4/2019 Addition Reaction of Carbonyl

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ADDITION REACTION OF CARBONYL

Elgaliza Karina Devi (4301409046)

Yohanna Indah S. (4301409062)

Ryandono Adhi K. (4301409069)


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Reaksi-reaksi Aldehid dan Keton

Karbonil bersifat polar sehingga dapat diserang olehNukleofilik (Nu:-) atau elektrofilik (E+)

Reaksi Umum

Faktor-faktor yang mempengaruhi reaktivitas aldehid / keton :

Muatan (+) pada karbon karbonil

Faktor stearik

Naiknya Reaktivitas

Reaksi Adisi

R

C

R

O

Nu

R

C

R

O

E

-+


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Nucleophilic Addition Reactions

In general, aldehydes are more reactive

towards nucleophilic additionreactions than ketones

inductive effect

steric effect


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1. The inductive effect

Alkyl groups are electron-releasing groups

The carbonyl carbon atom is less electron-deficient in ketones

less susceptible to nucleophilic attack


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2. The steric effect

In aldehydes,

one group being attached to the carbonyl

carbon atom is a small hydrogen atom

the carbonyl carbon atom of aldehydes is

less crowded

more susceptible to the attack of

nucleophiles


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2. The steric effect

In ketones,

the two alkyl or aryl substituents at thecarbonyl carbon atom cause a greater

steric hindrance to the nucleophiles fromapproaching the carbonyl carbon atom


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e.g. in pentan-3-one,


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Nucleophilic Addition ReactionsThe general order ofdecreasing reactivity of carbonyl

compounds towards nucleophilic addition

reactions is:

where R and R represent alkyl groups, and Ar

and Ar represent aryl groups


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Adisi dengan Air

ex :


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Adisi Alkohol


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Mekanism formation of acetal from hemiacetal


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Cyanide ion is able to attack the carbonyl carbon atom

more rapidly than HCN itself

Cyanide ion is a stronger nucleophile

The addition of HCN itself to the carbonyl group of

aldehydes and ketones takes place very slowly

HCN is a poor nucleophile

Adisi Nukleofolik HCN: Sianohidrin


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Produk Sianohidrin

Sintesis asam-asam amino

Contoh Mendelonitril (kelabang)


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Mekanisme Adisi Nukleofolik HCN: Sianohidrin

O

R'R

OH

CNR'R

HCN

suatu sianohidrin

Dengan HCN murni reaksi sangat lambat

Dengan penambahan sedikit basa atau ion sianida reaksi cepat

O

HC N

O

H

CN HO

H

CN

HCN

C N

Mandelonitril (88%)(suatu sianohidrin)

Benzaldehida


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Adisi Nukleofilik Pereaksi Grignard:

Pembentukan Alkohol

Pereaksi Grignard adalah nukleofil karena ikatan

karbon-magnesium sangat terpolarkan dengan

kerapatan elektron yang tinggi pada karbon

O O

R

OH

R

H3O+

R +MgX

+MgX

HOMgX

KarbonilIntermediattetrahedral

Alkohol


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#3 synthesis of alcohols. Used to build larger molecules from smaller organic

compounds.

RMgX +H

CH

O

RCH2OMgXH+

RCH2OH

formaldehyde1o alcohol + 1 C

RMgX +

R'C

H

OR'CHOMgX

R

H+R'CHOH

Rother aldehydes 2o alcohol + X C's


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R-MgX +R'

CR"

O R-COMgX

R'

R"

H+

R-COH

ketone

3

o

alcohol + X C's

RMgX +H2C CH2

ORCH2CH2OMgX

H+

RCH2CH2OH

ethylene oxide 1o alcohol + 2 C's

R'

R"


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Planning a Grignard synthesis of an alcohol:

a) The alcohol carbon comes from the carbonyl compound.

b) The new carbon-carbon bond is to the alcohol carbon.

C

O

+ RMgXH+

C

OH

RNew carbon-carbon bond

addition reaction of carbonyl

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