H1 NMR Flashcards
(10 cards)
What four aspects of the NMR spectra tell us about the structure?
Chemical shift
Chemical equivalent and non equivalent protons
Integration
Signal splitting
What is chemical equivalence?
Hydrogens in the same chemical environment.
Why do hydrogens in the same environment show only one signal?
They all have the same frequency when applied to a magnetic field.
What is chemical shift?
The x axis on a spectra, where it appears. Different environments have different shift.
What is the reference used in NMR?
TMS, tetramethylsilane.
Why is this reference used?
Si less electronegative than carbon. The H in TMS are in a high density environment, highly shielded with very low resonance frequency and rarely interferes with the signals of other compounds. Has 12 equivalent H so shows one strong signal.
What is integration?
The area under a signal. This is proportional to the number of protons in the signal.
What is signal splitting?
When there are more than one signals for an organic molecule.
What is a doublet and triplet?
When the signal is split into two with the integration 1:1.
When the signal is split into three with the integration 1:2:1.
