Proton NMR Spectrum of the Model Compound

The sample is introduced into the spectrometer, locked onto the deuter-ated solvent (here CDCl3) and the homogeneity optimized by shimming as described by the instrument manufacturer (this can often be done automatically, particularly when a sample changer is used). 

The proton experiment is a so-called single channel experiment the same channel is used for sample irradiation and observation of the signal, and the irradiation frequency is set (automatically) to the resonance frequency of the protons at the magnetic field strength used by the spectrometer. 

The precise measurement frequency varies slightly with solvent, temperature, concentration, sample volume and solute or solvent polarity, so that exact adjustment must be carried out before each measurement. This process, known as tuning and matching, involves variation of the capacity of the circuit. Modern spectrometers carry out such processes under computer control. 

The measurement procedure is known as the pulse sequence, and always starts with a delay prior to switching on the irradiation pulse. The irradiation pulse only lasts a few microseconds, and its length determines its power. The NMR-active nuclei (here protons) absorb energy from the pulse, generating a signal. 

To he a little technical the magnetization of the sample is moved away from the z-axis, and it is important to know the length of the so-called 90° pulse 

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Fig. 4 Proton NMR spectrum of the model compound 9DDA9 deuterated on the alkyl chain (spacer), 9DDA9-d2o, in the nematic phase at 89-5 C, on cooling. (S) represents the main contribution of the spacer to the proton spectrum, which has disappeared as a consequence of deuteration (a small contribution, S, remains due to incomplete deuteration). (For further details see Section 3.2.)...

For the determination of the methoxycarbonyl chain end fimctionality, a model compound was synthesized under similar conditions to that of the telechelic polymer. TMPCl was capped with DPE, followed by end quenching with MTSMP. This model compound was used for the assignments of both the H NMR and the NMR chemical shifts corresponding to the methoxycarbonyl chain end, as well as for calibration for IR measurements. The H NMR spectrum of the model compound is shown with the assignments in Figure 1. The peaks corresponding to protons c-i are... 

In the NMR spectrum of the ra-fused erythrinanone [155] the chemical shifts of the ethyl group protons are to low frequency of those in model compounds [156] as a result of the cw-relationship between the... 

The proton NMR spectrum of a copolymer obtained at — 78°C is shown in Figure 10. Two triplets of equal intensity centered at 5.93 and 7.62r were observed. There is no other resonance for this sample. On the basis of proton NMR spectra of model compounds (5), these two triplets may be assigned to two CH2 groups, as shown below. 

The NMR spectrum of the pure hydroxypropylated polystyrene showed peaks in the regions of d 21.5-26 ppm and d 64-67.5 ppm. Analysis by the attached proton test (APT) in conjunction with model compounds indicated that the region between 21.5 and 26 ppm corresponds to the methyl carbon resulting from attack of the polymeric organo-lithium at the least hindered carbon to form a secondary alcohol chain-end functional group (see (a) in eqn [7]). The area between 3 64 and 67.5 ppm was assigned to the carbon bonded to oxygen for two diastereomerically different products as shown by structure 1, where the chiral carbon atoms are labeled with asterisks. 

In the H—NMR-spectrum of compound 4144 44b an AA BB multiplet is found at the unexpected 5-value of 6.39 ppm it is assigned to the triphenylethane arene protons, which, according to molecular models, come to lie in the shielding region of an opposing phenylene ring of the triphenylbenzene unit. 

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