REAKSI ALKIL HALIDA :SUBSTITUSI NUKLEOFILIK

DAN ELIMINASIOleh : Alvan Febrian Shalas, S. Farm., Apt

TUJUAN PEMBELAJARAN Mahasiswa dapat memahami Mekanisme dan Karakteristik reaksi :1. SN12. SN23. E14. E2

“Alkyl halides do one of two things when they react with a nucleophile/base, such as hydroxide ion: either they undergo substitution of the X

group by the nucleophile, or they undergo elimination of HX to yield an alkene”

REAKSI SN2

SUBSTITUSINUKLEOFILIKBIMOLEKULAR

KARAKTERISTIK

INVERSI KONFIGURASI

REAKSI ORDE KEDUA

SINGLE STEP

REAKSI SN2MEKANISME REAKSI

REAKSI SN2REAKSI ORDE KEDUA

The rate of reaction is linearly dependent on the

concentrations of two species

Alkil halida

Nukleofil

REAKSI SN2SN2 REACTION RATE

SUBSTRAT

NUKLEOFIL

LEAVING GROUP

SOLVENT

REAKSI SN2SUBSTRAT

STERIC HINDRANCE REACTION RATE

REAKSI SN2

REAKSI SN2

NUKLEOFIL

NUKLEOFILISITAS REACTION RATE

REAKSI SN2NUKLEOFILISITAS

REAKSI SN2NUKLEOFILISITAS

• Nucleophilicity roughly parallels basicity when comparing nucleophiles that have the same reacting atom. Thus, OH- is both more basic and more nucleophilic than acetate ion, CH3CO2 -, which in turn is more basic and more nucleophilic than H2O

• Nucleophilicity usually increases going down a column of the periodic table. Thus, HS - is more nucleophilic than HO -, and the halide reactivity order is I - > Br - > Cl –

• Negatively charged nucleophiles are usually more reactive than neutral ones

REAKSI SN2

LEAVING GROUP

STABILISASI MUATAN (-) pd TRANSITION

STATE REACTION RATE

REAKSI SN2

SOLVENT

GROUND STATE ENERGY OF NU

POLAR PROTIC SOLVENT

(CONTAIN –OH; –NH)

REACTION RATE

POLAR APROTIC SOLVENT

REAKSI SN2

SOLVENT

• DMSO : Dimetilsulfoksida• DMF : Dimetilformamida• HMPA : Heksametilfosforamida

REAKSI SN2

SN1

SUBSTITUSI NUKLEOFILIK

UNIMOLEKULAR

KARAKTERISTIK

REAKSI ORDE PERTAMA

PRODUK CAMPURAN RASEMAT

TWO STEPS

SN1

TWO STEPS

SN1

MEKANISME REAKSI

SN1

the SN1 reaction has a rate that depends only on the alkyl halide concentration and is independent of the

nucleophil concentration. In other words, the reaction is a first-order process; the concentration of

the nucleophile does not appear in the rate equation.

REAKSI ORDE PERTAMA

SN1

SN1 REACTION RATE

SUBSTRAT

NUKLEOFIL

LEAVING GROUP

SOLVENT

SN1

SUBSTRAT

STABILITAS KARBOKATION REACTION RATE

1o

2o

3o

SN1

LEAVING GROUP

Good leaving groups increase the reaction rate by lowering the energy level of the

transition state for carbocation formation.

SN1

NUKLEOFIL

“the nucleophile does not affect an SN1 reaction”

SN1

SOLVENT

Solvent molecules orient around the carbocation so that the electron rich ends of the solvent dipoles face the positive charge, thereby lowering the energy of the ion and favoring its formation

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SN vs E

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