Download - EFEK INDUKSI
![Page 1: EFEK INDUKSI](https://reader035.vdokumen.com/reader035/viewer/2022062305/56816348550346895dd3d973/html5/thumbnails/1.jpg)
EFEK INDUKSIKIMIA ORGANIK FISIK
![Page 2: EFEK INDUKSI](https://reader035.vdokumen.com/reader035/viewer/2022062305/56816348550346895dd3d973/html5/thumbnails/2.jpg)
MENGAPA TINGKAT KEASAMANNYA BERBEDA ?
C-CH2O-HH
HH
C-CH2O-HF
FF
EthanolpKa 15.9
2,2,2-TrifluoroethanolpKa 12.4
H CO
O HC
O
O HH3C C
O
O HH2C
FpKa 3,75 4,75 2,66
![Page 3: EFEK INDUKSI](https://reader035.vdokumen.com/reader035/viewer/2022062305/56816348550346895dd3d973/html5/thumbnails/3.jpg)
Mengapa Tingkat Kebasaannya Berbeda ?•H-NH2 pKb = 4,75
•CH3-NH2 pKb = 3,34
![Page 4: EFEK INDUKSI](https://reader035.vdokumen.com/reader035/viewer/2022062305/56816348550346895dd3d973/html5/thumbnails/4.jpg)
Mengapa laju reaksi nitrasi pada senyawa berikut berbeda ?
![Page 5: EFEK INDUKSI](https://reader035.vdokumen.com/reader035/viewer/2022062305/56816348550346895dd3d973/html5/thumbnails/5.jpg)
Asam metanoat lebih asam dari asam etanoat karena pada asam etanoat terdapat gugus metil yang mempunyai kemampuan mendorong elektron ikatan melalui ikatan sigma (C-C-O-H) sehingga atom O menjadi relatif makin negatif, akibatnya atom H sukar lepas sebagai H+, asamnya menjadi lebih lemah. Gugus CH3 mempunyai efek induksi mendorong elektron, diberi simbol +I.
Asam alfamonoflouroetanoat lebih asam dari asam metanoat karena pada asam alfa monoflouroetanooat terdapat gugus F yang mempunyai kemampuan menarik elektron ikatan melalui ikatan sigma sehingga atom O menjadi relatif makin positif, akibatnya atom H makin mudah lepas sebagai H+, asamnya menjadi lebih kuat.Gugus F mempunyai efek induksi menarik elektron diberi simbol -I
![Page 6: EFEK INDUKSI](https://reader035.vdokumen.com/reader035/viewer/2022062305/56816348550346895dd3d973/html5/thumbnails/6.jpg)
Inductive Effects
• An inductive effect is the pull of electron density through bonds caused by electronegativity differences in atoms.
In the example below, when we compare the acidities of ethanol and
2,2,2-trifluoroethanol, we note that the latter is more acidic than the
former.
![Page 7: EFEK INDUKSI](https://reader035.vdokumen.com/reader035/viewer/2022062305/56816348550346895dd3d973/html5/thumbnails/7.jpg)
• The reason for the increased acidity of 2,2,2-trifluoroethanol is that the three electronegative fluorine atoms stabilize the negatively charged conjugate base.
Inductive Effects
![Page 8: EFEK INDUKSI](https://reader035.vdokumen.com/reader035/viewer/2022062305/56816348550346895dd3d973/html5/thumbnails/8.jpg)
Inductive Effects
• When electron density is pulled away from the negative charge through bonds by very electronegative atoms, it is referred to as an electron withdrawing inductive effect.
• More electronegative atoms stabilize regions of high electron density by an electron withdrawing inductive effect.
• The more electronegative the atom and the closer it is to the site of the negative charge, the greater the effect.
• The acidity of H—A increases with the presence of electron withdrawing groups in A.
![Page 9: EFEK INDUKSI](https://reader035.vdokumen.com/reader035/viewer/2022062305/56816348550346895dd3d973/html5/thumbnails/9.jpg)
Electron-withdrawing inductive effect▫The polarization of electron density of a
covalent bond due to the electronegativity of an adjacent covalent bond.
C-CH2O-HH
HH
C-CH2O-HF
FF
EthanolpKa 15.9
2,2,2-TrifluoroethanolpKa 12.4
![Page 10: EFEK INDUKSI](https://reader035.vdokumen.com/reader035/viewer/2022062305/56816348550346895dd3d973/html5/thumbnails/10.jpg)
•+ I menunjukkan kemampuan suatu gugus untuk mendorong/menolak elektron lebih kuat dari atom H
•-I menunjukkan kemampuan suatu gugus untuk menarik elektron lebih kuat dari atom H
•Efek induksi bekerja melalui ruang dan ikatan sigma. Makin jauh letak gugus/atom yang memiliki efek induksi, makin kecil pengaruhnya terhadap polarisai ikatan.
![Page 11: EFEK INDUKSI](https://reader035.vdokumen.com/reader035/viewer/2022062305/56816348550346895dd3d973/html5/thumbnails/11.jpg)
CF3-CH2-OH CF3-CH2-CH2-OH CF3-CH2-CH2-CH2-OH2,2,2-Trifluoro-
ethanol(pKa 12.4)
3,3,3-Trifluoro-1-propanol(pKa 14.6)
4,4,4-Trifluoro-1-butanol
(pKa 15.4)
Stabilization by the inductive effect falls off rapidly with increasing distance of the electronegative atom from the site of negative charge in the conjugate base.
![Page 12: EFEK INDUKSI](https://reader035.vdokumen.com/reader035/viewer/2022062305/56816348550346895dd3d973/html5/thumbnails/12.jpg)
▫Posisi gugus menentukan besarnya efek induksi yang diberikan.
Butanoic acid
pKa 4.82
4-Chlorobutanoicacid
pKa 4.52
3-Chlorobutanoicacid
pKa 3.98
2-Chlorobutanoicacid
pKa 2.83
OH
O
OH
O
OH
O
OH
O
Cl
ClCl
![Page 13: EFEK INDUKSI](https://reader035.vdokumen.com/reader035/viewer/2022062305/56816348550346895dd3d973/html5/thumbnails/13.jpg)
•P-kresol dan fenol, mana yang lebih asam?
•pKa = 9,94 dan 10,19
![Page 14: EFEK INDUKSI](https://reader035.vdokumen.com/reader035/viewer/2022062305/56816348550346895dd3d973/html5/thumbnails/14.jpg)
Pengaruh Efek Induksi Terhadap Reaktivitas Reaksi
![Page 15: EFEK INDUKSI](https://reader035.vdokumen.com/reader035/viewer/2022062305/56816348550346895dd3d973/html5/thumbnails/15.jpg)
![Page 16: EFEK INDUKSI](https://reader035.vdokumen.com/reader035/viewer/2022062305/56816348550346895dd3d973/html5/thumbnails/16.jpg)
Pengaruh Efek Induksi pada Momen Dipol
C
C
H CH3
H CH3
momen dipol = 0,4 D
bp = 4oC
C
C
H CH3
H3C H
momen dipol = 0
bp = 1oC
C
C
H Cl
Cl H
momen dipol = 0
bp = 48oC
C
C
H
Cl H
momen dipol = 1,84 D
bp = 60oC
Cl
![Page 17: EFEK INDUKSI](https://reader035.vdokumen.com/reader035/viewer/2022062305/56816348550346895dd3d973/html5/thumbnails/17.jpg)
Manakah yang mempunyai momen dipol lebih besar ? (1,97 dan 1,71 D)
C
C
H
CH3 H
Cl
C
C
H Cl
CH3 H