REAKSI ELIMINASI PELEPASAN MOLEKUL YZ DARI ATOM-ATOM C BERDAMPINGAN DLM SUATU MOLEKUL PEREAKSI. DEHIDROHALOGENASI DAN DEHIDRASI 09/04/2017.

Presentasi berjudul: "REAKSI ELIMINASI PELEPASAN MOLEKUL YZ DARI ATOM-ATOM C BERDAMPINGAN DLM SUATU MOLEKUL PEREAKSI. DEHIDROHALOGENASI DAN DEHIDRASI 09/04/2017."— Transcript presentasi:

1 REAKSI ELIMINASI PELEPASAN MOLEKUL YZ DARI ATOM-ATOM C BERDAMPINGAN DLM SUATU MOLEKUL PEREAKSI. DEHIDROHALOGENASI DAN DEHIDRASI 09/04/2017

2 DEHIDROHALOGENASI ALKIL HALIDA
PELEPASAN/ PENARIKAN HX DARI ATOM-2 C BERDAMPINGAN DLM SEBUAH ALKIL HALIDA DILAKUKAN DG BASA KUAT MISALNYA: CH3ONa, C2H5ONa DAN (CH3)3COK 09/04/2017

3 DEHIDROBROMINASI ALKIL BROMIDA
CONTOH DEHIDROBROMINASI ALKIL BROMIDA 09/04/2017

4 DEHIDRASI ALKOHOL PELEPASAN/ PENARIKAN H2O DARI ATOM-2 C BERDAMPINGAN DLM SEBUAH ALKOHOL DILAKUKAN DG ASAM KUAT MISALNYA: H2SO4 DAN H3PO4 09/04/2017

5 MEKANIME REAKSI ELIMINASI
REAKSI ELIMINASI BIMOLEKULER (E2) r = k [R-X].[:B-] r = k [CH3CHBrCH3].[C2H5O-] REAKSI ELIMINASI UNIMOLEKULER (E1) r = k [R-X] r = k [(CH3)3C-Cl] 09/04/2017

6 REAKSI E2 DEHIDROBROMINASI ISOPROPIL BROMIDA DG LARUTAN NATRIUM ETOKSIDA DLM ETANOL   09/04/2017

7 MEKANISME REAKSI E2 BASA MENYERANG AT. H  DARI ARAH BERLAWANAN DG X (Br) AT . X (Br)  PERGI DR ARAH BERLAWANAN DG BASA SBG ION X- (Br-) AT-2 C  DAN  MEMBENTUK IKATAN RANGKAP MENGHASILKAN ALKENA 09/04/2017

8 REAKSI E1 DEHIDROBROMINASI t-BUTIL BROMIDA DG LARUTAN NATRIUM ETOKSIDA DLM ETANOL 09/04/2017

9 MEKANISME REAKSI E1 ALKIL HALIDA MENGALAMI IONISASI MENGHASILKAN ION KARBONIUM BASA MENYERANG AT. H  AT C  MEMBENTUK IKATAN RANGKAP DENGAN AT. C  MENGHASILKAN ALKENA 09/04/2017

10 PD HALIDA 3o KENAIKAN T TERJADI REAKSI E2
KOMPETISI SN2 DAN E2 PD HALIDA 3o KENAIKAN T TERJADI REAKSI E2 09/04/2017

11 KERUAHAN BASA PEREAKSI
KERUAHAN BASA PEREAKSI MENDORONG REAKSI ELIMINASI 09/04/2017

12 KEBASAAN BASA LEMAH SPT Cl-, CH3COO-, Br-, I- MENDORONG SN2
BASA KUAT: C2H5O-, OH-, NH2- MENDORONG E2 09/04/2017

13 KOMPETISI SN2 DAN E2 REAKSI SN2 MELIBATKAN BASA LEMAH, BASA SEDERHANA DLM PELARUT POLAR, DAN SUHU RENDAH REAKSI E2 MELIBATKAN BASA KUAT, BASA MERUAH, DLM PELARUT POLAR, DAN SUHU TINGGI. 09/04/2017

14 BAGAIMANA KOMPETISI SN1 DAN E1
REAKSI E1 MELIBATKAN KARBOKATION STABIL, BASA LEMAH, PELARUT POLAR DAN SUHU TINGGI REAKSI SN1 MELIBATKAN KARBOKATION STABIL, BASA LEMAH, PELARUT POLAR DAN SUHU RENDAH 09/04/2017

15 ATURAN ZAITSEV DEHIDROBROMINASI 2-BROMO-2-METILBUTANA DG NATRIUM ETOKSIDA REAKSI ELIMINASI TERJADI DG MEMBERIKAN ALKENA YG LEBIH TERSUBSTITUSI.   09/04/2017

16 BUKTI LAIN ATURAN ZAITSEV
DEHIDROKLORINASI NEOMENTIL KLORIDA DAN MENTIL KLORIDA DG NATRIUM ETOKSIDA 09/04/2017

17 ANTI ZAITSEV DEHIDROBROMINASI 2-BROMO-2-METILBUTANA DG KALIUM t-BUTOKSIDA ELIMINASI DG BASA MERUAH MEMBERIKAN ALKENA YG KURANG TERSUBSTITUSI.   09/04/2017

18 BAGAIMANA KOMPETISI SN1 DAN E1
REAKSI E1 MELIBATKAN KARBOKATION STABIL, BASA LEMAH, PELARUT POLAR DAN SUHU TINGGI REAKSI SN1 MELIBATKAN KARBOKATION STABIL, BASA LEMAH, PELARUT POLAR DAN SUHU RENDAH 09/04/2017

19 PROBLEM 1 WHEN CIS -1-BROMO-4-tert-BUTYLCYCLOHEXANE IS TREATED WITH SODIUM ETHOXIDE IN ETHANOL, IT REACT RAPIDLY. THE PRODUCT IS 4-tert-BUTYLCYCLOHEXENE. UNDER THE SAME CONDITIONS, TRANS-1-BROMO-4-tert-BUTYLCYCLOHEXANE REACTS VERY SLOWLY. WRITE CONFORMATIONAL STRUCTURE AND EXPLAIN THE DIFFERENCE IN REACTIVITY OF THIS CIS-TRANS ISOMERS. 09/04/2017

20 REAKSINYA 09/04/2017

21 JAWAB PROBLEM 1 PD ISOMER CIS TERDAPAT 2 AT H  DG POSISI AKSIAL, BEGITU JUGA Br BERADA PD POSISI AKSIAL SHG REAKSI E2 BERLANGSUNG LEBIH CEPAT. PD ISOMER TRANS BAIK AT H  MAUPUN Br YG AKAN BEREAKSI DLM POSISI EQUATORIAL, SEHG MENYEBABKAN REAKSI E2 SANGAT LAMBAT (SULIT). 09/04/2017

22 REAKSINYA 09/04/2017

23 PROBLEM 2 A). When cis-1-bromo-2-methylcyclohexane undergoes an E2 reaction, two product (cycloalkenes) are formed. What are these two cycloalkenes, and which would you expect to be the major product? Write conformational structures showing how each is formed. B) When trans-1-bromo-2-methylcyclohexane reacts in an E2 reaction, only one cycloalkene is formed. What is this product? Write conformational structures showing why is the only product. 09/04/2017

24 KESIMPULAN CH3X METIL RCH2X (1o) (R)2CHX (2o) (R)3CX (3o)
REAKSI BIMOLEKULER SN1/E1/E2 MEMBERIKAN REAKSI SN2 MEMBERI SN2, KECUALI DG BASA MERUAH MEMBERI REAKSI E2 MEMBERIKAN REAKSI SN2 DG BASA LEMAH DLM SOLVOLISIS BEREAKSI SN1/E1, PD T RENDAH SN1 DOMINAN MEMBERIKAN REAKSI E2 DG BASA KUAT BASA KUAT REAKSI E2 DOMINAN 09/04/2017

25 A BIOLOGICAL NUCLEOPHILIC SUBSTITUTION REACTION: BIOLOGICAL METHYLATION
THE CELLS OF LIVING ORGANISMS SYNTHESIZE MANY OF THE COMPOUNDS THEY NEED FROM SMALLER MOLECULES. A NUMBER OF REACTIONS TAKE PLACE IN THE CELLS OF PLANTS AND ANIMALS THAT INVOLVE THE TRANSFER OF A METHYL GROUP FROM AN AMINO ACID CALLED METHIONINE TO SOME OTHER COMPOUND. 09/04/2017

26 SOME OF THE COMPOUNDS THAT GET THEIR METHYL GROUP FROM METHIONINE
09/04/2017

27 METHYL TRANSFER MECHANISM
09/04/2017

28 BIOSYNTHESIS OF CHOLINE
09/04/2017

29 DEHIDRASI ALKOHOL PELEPASAN H2O DR ALKOHOL-2 MELALUI PEMANASAN DG ASAM KUAT ASAM BRONSTED: H2SO4 DAN H3PO4 ASAM LEWIS: ALUMINA (Al2O3) DLM INDUSTRI REAKSI DEHIDRASI ALKOHOL MENUNJUKKAN BBP KARAKTERISTIK PENTING. 09/04/2017

30 KONDISI REAKSI ALKOHOL PRIMER MEMERLUKAN ASAM PEKAT DAN SUHU TINGGI
09/04/2017

31 CAMPURAN ALKENA BBP ALKOHOL TERDEHIDRASI MEMBERIKAN HASIL CAMPURAN ALKENA MENGIKUTI ATURAN ZAITZEV 09/04/2017

32 PENATAAN ULANG BBP ALKOHOL 1o DAN 2o MENGALAMI PENATAAN ULANG SELAMA DEHIDRASI 09/04/2017

33 MEKANISME UMUM DEHIDRASI ALKOHOL TERKATALISIS ASAM
MENGIKUTI MEKANISME E1 09/04/2017

34 MEKANISME PENATAAN ULANG
PENATAAN ULANG SELAMA DEHIDRASI DARI 3,3-DIMETIL-2-BUTANOL 09/04/2017

35 FINAL PRODUCT 09/04/2017

36 BEBERAPA PERGESERAN DLM PENATAAN ULANG ION KARBONIUM
09/04/2017

37 DEBROMINATION OF VICINAL DIBROMIDES
VIC-DIBROMIDES UNDERGO THE LOSS OF A MOLECULE OF BROMINE (Br2)WHEN THEY ARE TREATED WITH A SOLUTION OF SODIUM IODIDE IN ACETON OR MIXTURE OF ZINC DUST IN ETHANOL. DEBROMINATION BY SODIUM IODIDE TAKE PLACE BY AN E2 MECHANISM. 09/04/2017

38 THE MECHANISM OF DEBROMINATION
09/04/2017

39 PROBLEM 1 Although ethyl bromide and isobutyl bromide are both primary halides, ethyl bromide undergoes SN2 reactions more than ten times faster than isobutyl bromide. When each compound is treated with a strong base (CH3CH2O-), isobutyl bromide gives a greater yield of elimination products than substitution products, whereas with ethyl bromide this behavior is reversed. What factor accounts for these results? 09/04/2017

40 PROBLEM 2 Consider the reaction of I- with CH3CH2Cl. (a). Would you expect the reaction to be SN1 or SN2? The rate constant for the reaction at 60o is 5x10-5 liter mole-1 sec-1. (b). What is the reaction rate if [I-] = 0.1 mole liter-1 and [CH3CH2Cl] = 0.1 mole liter-1? (c). If [I-] = 0.1 mole liter-1 and [CH3CH2Cl] = 0.2 mole liter-1? (d). If [I-] = 0.2 mole liter-1 and [CH3CH2Cl] = 0.1 mole liter-1? (e). If [I-] = 0.2 mole liter-1 and [CH3CH2Cl] = 0.2 mole liter-1? 09/04/2017

41 PROBLEM 3 When tert-butyl bromide undergoes SN1 hydrolisis, adding a “common ion” (i.e NaBr) to the aqueous solution has no effect on the rate. On the other hand when (C6H5)2CHBr undergoes SN1 hydrolisis, adding NaBr retards the reaction. Given that the (C6H5)2CH+cation is known to be much more stable than the (CH3)3C+ cation, provide an explanation for the different behavior of the two compounds. 09/04/2017