What are Diastereotopic groups in NMR?

The stereochemical term diastereotopic refers to the relationship between two groups in a molecule which, if replaced, would generate compounds that are diastereomers. Diastereotopic groups are often, but not always, identical groups attached to the same atom in a molecule containing at least one chiral center.

Can carbons be Diastereotopic?

When you have two hydrogens attached to a single carbon, they can have three different types of relationships. We call them “homotopic”, “enantiotopic”, and “diastereotopic”.

How can you tell if two protons are Diastereotopic?

The most common set of nonequivalent protons that you will hear bout in your course is going to be the diastereotopic protons. If replacing two protons with a different group (X) gives a pair of diastereomers, the protons are called Diastereotopic.

Can NMR distinguish diastereomers?

Diastereomers have different electronic structure and therefore can be distinguished with NMR spectroscopy. So, what you do is to find a chiral auxiliary to use it as a CDA to react with your compound of interest.

Which compound contains Diastereotopic protons?

1,2-dichloropropane
These hydrogen atoms are diastereotopic and are chemically non-equivalent. Diastereotopic protons will give different signals in the spectrum. Diastereomerism also occurs in saturated acyclic compounds; for example, 1,2-dichloropropane is a simple compound that contains diastereotopic protons.

What is Enantiotopic and Diastereotopic?

Enantiotopic faces, atoms or groups look the same on their own, but will react differently with chiral molecules. Diastereotopic faces, atoms or groups always appear different.

How is a spectrum obtained in NMR spectroscopy?

An nmr spectrum is acquired by varying or sweeping the magnetic field over a small range while observing the rf signal from the sample. An equally effective technique is to vary the frequency of the rf radiation while holding the external field constant.

How do you analyze a 13 C NMR spectrum?

In general, when you state analyzing a 13 C NMR, split the spectrum in two parts by drawing a line at 100 ppm; below this value you have the saturated functional groups, and beyond that is the unstructured region. So, saturated carbon atoms connected to electronegative heteroatoms give signal from 30-90 ppm.

What is chiral derivatizing agents NMR spectroscopy?

Chiral Derivatizing Agents NMR Spectroscopy Enantiomer Determination 1) Polar or bulky group to fix a particular conformation 2) A functional group to allow for attachment of substrate 3) A group able to produce an efficient and space-oriented anisotropic effect – Shields/deshields L1and L2in each diastereomer Chiral Derivatizing Agents

Why is carbon-carbon coupling not observed in NMR?

Carbon-carbon coupling is not observed because of the low abundance of the 13C isotope. Remember, the most abundant natural isotope of carbon is the 12 C which, having an even number of protons and neutrons is not magnetically active and cannot be used in NMR.

Is it possible to have singlets in 13C NMR with carbon nucleus?

Carbon nucleus resonates at a different frequency range than proton does, which makes it possible to have all the signals as singlets. However, you need to know that signal splitting in 13C NMR by neighboring hydrogens does occur which leads to complicated splitting patterns.