p 3spektrometriprotonnmr 130607220236 phpapp02

8/10/2019 p 3spektrometriprotonnmr 130607220236 Phpapp02

1/33


2/33

NMR ?

NUCLEAR MAGNETIC RESONANCE

ATAU

RESONANSI MAGNET INTI

H-NMR C-NMR


3/33

Kegunaan H-NMR?

Memberikan gambaran mengenai :1. Jenis hidrogen

2. Jumlah hidrogen

3. Lingkungan hidrogen dalamsuatu senyawa


4/33

Prinsip dasar H-NMR?

NMR didasarkan pada penyerapan

gelombang radio oleh inti inti

tertentu dalam molekul organik,

apabila molekul tersebut berada dalammedan magnet yang kuat


5/33

Fenomena Resonansi Magnetik Inti

Model fisika klasik:

Inti atom bermuatan positif dan berputar pada porosnya

(spin)

membentuk medan magnet yang berputar

penempatan di dalam suatu medan magnet (Bo)

menghasilkan putaran presesi yang menyerap di daerahgelombang radio

frekuensi presesi dinyatakan oleh:


6/33


7/33

Proses terjadinya resonansi?


8/33

When molecules containing hydrogen atoms areplaced in an external magnetic field ; the

magnetic moment of each proton nucleus

aligns itself in one of two different

orientations:


9/33

The parallel protons absorb energy (radio

waves) and the magnetic moment turnaround (flip) to the high energy antiparallelstate (Resonance)


10/33

2 Cara agar terjadi resonansi?

Bo tetap,

frekuensi radiasielektromagnetik

diubah - ubah

frekuensi radiasi

elektromagnetiktetap, Bo diubah

ubah sampai

dicapai resonansi,

Lebih memuaskan


11/33

Bentuk spektrum NMR?


12/33

12

The spectrum is measured on a delta (d) scale in units

of parts per million (ppm)

Lower frequency is to the left in the spectrum; theseabsorptions are said to be downfield

Higher frequency is to the right in the spectrum:

these absorptions are said to be upfield

The small signal at d0 corresponds to an internal

standard called tetramethylsilane (TMS) used to

calibrate the chemical shift scale

The number of signals in the spectrum correspondsto the number of unique sets of protons


13/33

Pergesaran Kimia?

Perbandinganantara letak resonansi

suatu proton tertentu dengan letak

resonansiproton standar


14/33

14

Chemical Shift

Chemical shifts are measured in relation to the

internal reference tetramethylsilane (TMS) The protons of TMS are highly shielded because of the

strong electron donating capability of silicon

Thed

scale for chemical shifts is independent ofthe magnetic field strength of the instrument

(whereas the absolute frequency depends on field

strength)


15/33

Ada apa dengan

TMS?

1. TMS mempunyai dua belas proton yang setara

kimia,karenya memberikan satu puncak tunggal

2. TMS merupakan cairan yang volatil, dapat ditambahkan

dalam jumlah sedikit pada larutan sampel dalam

pelarutnya, sampel dapat diperoleh kembali dengan

menguapkan pelarutnya

3. Proton pada hampir semua senyawa organik mengalamiresonansi pada medan yang lebih rendah daripada proton

TMS

4. TMS bersifat inert dan tidak larut dalam air


16/33

Faktor yang mempengaruhipergesaran kimia?


17/33

Faktor intramolekular

1. Efek induksi

2. Efek anisotropi

3. Efek mesomeri

Faktor intermolekuler

1. Ikatan hidrogen

2. Temperatur

3. Pelarut


18/33

18

Fields induced by sigma bonds

The induced field from circulating sigma bond

electrons opposes Hoin the vicinity of proton


19/33

19

A proton that is bonded to the same carbon as an

electronegative atom is more deshielded than proton

on other carbons. (Inductive Effect)

H3C-F H3C-ClH3C-Br H3C-I

d 4.3 d 3.0 d 2.7 d 2.1

Increased shielding of H

C F

H

H

H

F causes a decrease in

e density around each atom


20/33

20

The inductive effect

C

H

H

H

C

H

H

C

H

H

X effect of X is importantin decreasing e densityaround this proton

effect of X is oflittle importancein decreasinge density around

this proton

Si

CH3

CH3

CH3

CH3

greater e density on H:highly shielded

Tetramethylsilane(TMS)


21/33

21

Summary of induced field effects


22/33

22

Equivalent and nonequivalent protons

MENGHITUNG PROTON


23/33

23

CH3CH2OCH2CH3six equivalent protons

four equivalent protons


24/33

24

C

CH3CH

3 H

Br six equivalent protons

CH3

CH3

CH3 Br six equivalent protonstwo


25/33

25

Spin-spin coupling

Protons that split each other signals are said

to have undergone spin-spin coupling


26/33

26

n+1 Rule

The number of peaks of a particular proton is

equal to number (n) of nonequivalent protons

on the adjacent atoms + 1


27/33

27


28/33

28

Notice:


29/33

29

Splitting pattern:

The singlet

If no neighboring nonequivalent protons present

one single peak (singlet) (S).

eg.CH3 Cl CH3OCCH3

O

CCH3

CH3

Br

CH3 H

H

H

H

HH


30/33

30

The doublet

If oneneighboring nonequivalent proton present

two peaks (doublet) (d).

eg

CH3 C

H

ClCl

CH3 C

H

Cl

CH3

OCH3

HH

CH3

H H

C C

HH

Cl Cl Cl Cl

equivalent H's => S


31/33

31

The triplet

If twoneighboring nonequivalent protons present

three peaks (triplet) (t).

eg

CH3CH2Cl C CHHClCl Cl

H

ClCH2CH2OCH3


32/33

32

The quartet

If a proton is neighboring to CH3it will observe

3+1=4 peaks (quartet) (q)

eg

CH3CH2Cl CH3CHCl2

CH3CH2OCH2CH3


33/33

33

p 3spektrometriprotonnmr 130607220236 phpapp02

Documents