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Organic&bio. chem


Do all nuclei have spin? No, only select nuclei have spin.
Da all nuclei have charge? Yes, all nuclei have charge.
What produces a magnetic field? A spinning, charged nucleus.
What is I? Spin quantum number.
Calculating I: EVEN + EVEN I= 0, can't use for NMR
Calculating I: EVEN + ODD I = 1/2, 3/2, 5/2, ...
Calculating I: ODD + ODD I = 1,2,3.....
In the spectrometer's magnet, the spins will align: With or against the magnetic field. The two possibile spin states have different energies. (alpha low beta high)
The separation of a and B spin-states depends on: The strength of the spectrometer's magnet.
ΔE = What is ɣ? hv = h*(ɣ/2π)*Bo ɣ = gyromagnetic ratio
Resonance Frequencies for different nuclides are proportional to: their gyromagnetic ratios (ɣ)
Continuous Wave NMR. RF source: Protons: Irradiating RF source: low amplitude, fixed frequency, applied continuously. Spactrum trace recorded while magnetic field swept. Protons w/ different resonance freq. come into resonance sequentially. Slow!
Fourier Transform NMR. RF sources: Proton excitation: Time: Short, powerful RF pulse. Excites protons w/ different resonance frequencies all at once (like a piano) Spin signals recorded vs. time when pulse is switched off.
What is the chemical shift? Small changes in the resonance frequency due to shielding from the surrounding electrons.
δ(ppm) = (Δν [Hz])/(Spectrometer operating frequency [MHz] )
TMS: tetramethylsilane - soluble in most organic solvents.
what is the purpose of a δ scale? To make chemical shifts independent of the spectrometer's magnetic field.
For (1)H spectra, peak area is proportional to: proportional to # of protons.
In the n+1 rule, what is n? # of equally coupled protons.
What names are given to a carbon relative to the ipso carbon in order: ortho, meta, para.
What does DEPT experiment stand for? Distortionless, Enhancement, by Polarization Transfer.
What does DEPT do? Enhances the intensity of signals, Provides information on the number of protons attached, Quarternary carbons are not observed.
In DEPT 135° pulse means: Positive signals for CH and CH3 groups. Inverted signals for CH2.
In DEPT 90° pulse means: Positive signals for CH groups. Null signals for CH2 and CH3
In DEPT 45° pulse means: Positive signals for CH CH2 and CH3
δ(Cipso)= 128.5 + δipso + E(δortho) + E(δmeta) + E(δpara)
Created by: Liarna9Joy



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