Organic synthesis, NMR and chromatography GapFill

Nuclear magnetic resonance (NMR) involves placing a sample in   a magnetica gravitationalan opticalan electric field, then bombarding it with electromagnetic waves from the  microwaveradioultravioletinfrared region. The resulting spectra have a quantity called chemical shift on their x-axes. Chemical shift has units of  parts per million (ppm)parts per dozen (ppd)parts per billion (ppb)parts per hundred (pph), and is represented by the symbol  πσαδ. The chemical shift of a nucleus is related to the electron density surrounding it: the higher the electron density, the lower the chemical shift. Nuclei with a high electron density around them are said to be  shieldedsheltereddefendedprotected.

¹H (proton) spectra offer more information than ¹³C spectra. Firstly, protons show spin-spin  couplingadditionlinkingpairing, causing signals to split according to the  2n+1n+22n+2n+1 rule. This gives information on the number of protons attached to adjacent carbon atoms. Furthermore,  differentiatedtalliedcubedintegrated ¹H spectra display the relative area under each signal, which corresponds to the relative number of protons in each environment.

Chromatography allows chemists to separate and, in some cases, identify the components of a mixture. There are several types of chromatography, but all of them rely on the use of both a stationary phase and   a variablea mobilea liquida loose phase (sometimes referred to as the  fluentabluenteluentsequent in column chromatography). In general, separation occurs because each component in the mixture has a characteristic balance of solubility in the solvent and  lenityaffinitylatinityantipathy for the stationary phase, which is determined by molecular properties such as polarity. Gas chromatography (GC) is slightly different in that the solvent is replaced by an inert carrier gas, which pushes the vaporised mixture through a tube packed with the stationary phase. A gas chromatogram displays a  subventiondetentionindentionretention time for each component, which can be identified by comparing this value with those in a library of reference compounds. (A similar process, instead using   RSRFSFRQ values, allows compounds to be identified by thin-layer chromatography.)