NMR-Spectroscopy

The pharmaceutical institute is equiped with
a 300 MHz NMR spectrometer, a Bruker
Avance III 300, with a normal broadband
probe head for the measurement of a
great number of nuclei of samples in solution.
The automatic tuning and matching device
allows, together with the sample changer,
the recording of numerous spectra
in a routine manner

NMR-Device

 
  NMR-Console

  A simple molecule is used for demonstration:
  1-(4-fluorophenyl)ethanone semicarbazone,
  dissolved in DMSO-d6


1-(4-fluorophenyl)ethanone

 

  NMR probe head

  This compound has been reported for the first time in
  1995 by Dimmock et al. in a paper in the European
  Journal of Medicinal Chemistry:

  JR Dimmock, KK Sidhu, SD Tumber, SK Basran,
  M Chen, JW Quail, J Yang, I Rozas and DF Weaver:
  Some aryl semicarbazones possessing anticonvulsant
  activities, Eur. J. Med. Chem. 30, 1995, 287-301.

  Abstract: A number of aryl semicarbazones displayed
  anticonvulsant activity in the maximal electroshock (MES)
  and subcutaneous pentylenetetrazole (scPTZ) screens
  when administered intraperitoneally to mice. When given
  by the oral route to rats, protection was afforded in the
  MES but not scPTZ tests. Correlations were noted between
  the σ and σ* values of the aryl substituents, the interplanar
  angles made by the aryl rings with the adjacent carbimino
groups and the shapes of certain semicarbazones determined by X-ray crystallography, and the activities in the rat oral MES screen. Molecular modeling studies revealed a number of statistically significant descriptors which contributed to anticonvulsant activity.

-botttom of the the probe head

  See the 1H-NMR-spectrum

See the proton decoupled 13C NMR spectrum

See the proton coupled 19F-NMR spectrum

See the two dimensional 1H,15N correlation spectrum (HSQC)

See the See the two dimensional 1H,15N correlation spectrum (HMBC)

Go to the assignment page

NMR-Computer
     
  1H-NMR spectrum (300 MHz) of 1-4-Fluorophenyl-ethanon semicarbazon in DMSO-d6 Solvent signals at 2.5 ppm (DMSO-d5), about 3.3 ppm (water) and 0.0 ppm (not visible, internal standard TMS)
 
NMR_1H
  13C-NMR spectrum, proton decoupled (75 MHz) of 1-4-Fluorophenyl-ethanon semicarbazon
in DMSO-d6, internal standard TMS
 
13C-NMR spectrum
 

19F-NMR spectrum, proton coupled (282 MHz) of 1-(4-Fluorophenyl)ethanone semicarbazone
in DMSO-d6, internal standard CFCl3

 
19F-NMR spectrum
 

1H,15N-NMR- HSQC spectrum of 1-(4-Fluorophenyl)ethanone semicarbazone in DMSO-d6

 
1H,15N-NMR- HSQC spectrum
 

1H,15N-NMR- HMBC spectrum of 1-(4-Fluorophenyl)ethanone semicarbazone in DMSO-d6,
internal standard nitromethane

 
1H,15N-NMR- HMBC spectrum
 

Complete assignment and coupling constants

 
Complete assignment
  the protons of the aromatic ring form a n AA´XX´-multiplet, further split by the 3J and 4J fluorine proton couplings

Massenspektrometrie

 
  For mass spectrometric characterization and
quanifications we run electron impact mass
spectra with a HP ms engine (A). Samples can
be introduced via direct inlet probe and also
with GC-MS coupling.

The picture shows the EI-MS spectrum of 1-(4-
fluorophenyl)ethanone semicarbazone, the
fragmentation giving information about the
molecular structure.

Struktur1
HP5989_MS_Engine
 

EI-MS (70 eV), direct inlet probe = tungsten wire

EI-Mass-spectrum

   
  Complex mixtures of volatile
compounds will be separated by gas
chromatography ((HP 5890 Series II)
before ionization.

Particle Beam and Thermospary LC-
MS coupling techniques for the ms
engine are no longer in use.

Gaschromatograph_HP5890II
     
 

For LC-MS coupling we use an Agilent 1100 HPLC system with UV detector coupled to a Bruker Esquire ~LC. As ionization techniques either electrospray ionization (ESI) or atmosperic pressure chemical ionization (APCI) is available.

Agilent_1100_LC

  Bruker_Esquire