CW nmr spectrometer

NMR Measurements. 1H-NMR measurements were made at room temperature using a Varian T-60 CW-NMR spectrometer. 

An NMR spectrum is effectively a graph of the intensity of absorption of Rf radiation (y-axis) against the frequency of the Rf radiation (x-axis). Since frequency and magnetic field strength are linked by the Larmor equation, the x-axis could also be calibrated in units of magnetic field strength. In a CW NMR spectrometer, the x-axis of the output device (usually a pen plotter) is coupled to the frequency sweep so that the response of the sample is displayed as the frequency of the Rf transmitter varies. 

A CW NMR spectrometer (Figure 3.14) consists of a control console, magnet (typically electromagnets or permanent magnets are used), and two orthogonal coils (transmitter and sweep coils) of wire that serve as antennas for rf radiation. One coil is attached to an rf transmitter and the other coil is the rf amplifier (pickup) coil and is attached to the detection electronics. 

FIGURE 3.14 Schematic diagram of a CW NMR spectrometer. The tube is perpendicular to the z axis of the magnet A, sample tube B, transmitter coil C, sweep coils D, receiver coil E, magnet... 

Older continuous wave (cw) NMR spectrometers were designed to operate in one of two modes ... 

The general features of a CW NMR spectrometer were described briefly in Exp. 32, and details about Fourier-transform NMR instruments are given in Exp. 43. For the spectrometer you are to use, more specific operating instructions will be provided by the instructor. Obtain several milliliters each of acetylacetone (CH3COCH2COCH3, M= 100.13, density = 0.98 gcm ) and ethyl acetoacetate(CH3CH20COCH2COCH3, M= 130.14, density = 1.03 g cm ). Prepare small volumes of two solvents and three solutions. 

Conventional scanning (CW) nmr spectrometers take several minutes to scan a full-range spectrum which is said to be in the frequency domain (absorption... 

The area of each fjeak gives the relative number of protons and is produced directly on the spectrum (Fig. 29.6). On CW—NMR spectrometers the height of the peak area integration line must be measured using a ruler, whereas on FT-NMR machines the area is calculated and displayed as a number. You must remember that ... 

Procedure A—NMR Measurements Using a Continuous Wave (CW) NMR Spectrometer ... 

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