What is the Difference Between Betaine and Ylide

The key difference between betaine and ylide is that the atoms containing electrical charges are not always adjacent to each other in betaine, whereas these charged atoms are always adjacent to each other in ylides.

Although both betaine and ylides are chemical compounds containing electrically charged atoms, they are not similar. In other words, ylides are not betaines and betaines are not ylides.

1. Overview and Key Difference
2. What is Betaine
3. What is Ylide
4. Betaine vs Ylide in Tabular Form
5. Summary – Betaine vs Ylide

What is Betaine?

Betaine can be defined as a modified amino acid compound containing glycine with three methyl groups. Generally, these methyl groups can serve as methyl donors in several metabolic processes and are also useful in treating rare genetic causes of homocystinuria. We can abbreviate betaine as BET. It is an amino acid that has potential benefits for fighting heart diseases, improvement of body composition, and helping the promotion of muscle gain and fat loss.

Figure 01: Structure of Betaine

Betaine can be identified as a neutral chemical compound having a positive charged cationic functional group (e.g. quaternary ammonium cation, phosphonium cation, etc.) that does not bear a hydrogen atom and also contains a negatively charged functional group (e,g, carboxylate group) that is usually not adjacent to the cation. Therefore, we can identify betaine as a specific type of zwitterion.

Typically, in biological systems, there are naturally occurring betaines that serve as organic osmolytes. These compounds are synthesized inside organisms or are taken up from the environment through cells. The taking up of the compounds is helpful in protection against osmotic stress, drought, high salinity, or high temperature.

There are different uses of betaine: commercial uses as intermediates in Wittig reaction (phosphonium betaine) as components in polymerase chain reactions, as a supplement for bodybuilding, etc.

What is Ylide?

Ylide can be defined as a neutral dipolar molecule consisting of a formally negatively charged atom that is directly attached to a heteroatom having a formal positive charge. This type of compound has both these atoms with a full octet of electrons. The formally negative charged anion in a ylide is usually a carbanion. The heteroatom with a formal positive charge is usually nitrogen, phosphorous or sulfur.

Betaine and Ylide - Side by Side Comparison

Figure 02: Resonance Structures of a Phosphorous Ylide Compound

The structure of a ylide can be described as a chemical structure in which two adjacent atoms are connected to each other through both a covalent and an ionic bond. Usually, we can write the chemical formula as X+_Y-. Therefore, these are 1,2-dipolar compounds. It is also a subclass of zwitterions that appear mainly in organic chemistry as reagents and reactive intermediates.

The types of ylides include ylides based on phosphorous, sulfur, oxygen, and nitrogen. Apart from that, there are halonium ylides as well. These compounds can undergo chemical reactions such as dipolar cycloadditions, dehydrocoupling with silanes, Sigmatropic rearrangements, and allylic rearrangements.

What is the Difference Between Betaine and Ylide?

Although both betaine and ylides are chemical compounds containing electrically charged atoms, they are not similar. The key difference between betaine and ylide is that the atoms containing the electrical charges are not always adjacent to each other in betaine, whereas these charged atoms are always adjacent to each other in ylides.

The following table lists the differences between betaine and ylide in tabular form for side by side comparison.

Summary – Betaine vs Ylide

Betaine is a modified amino acid compound containing glycine with three methyl groups. Ylide is a neutral dipolar molecule consisting of a formally negatively charged atom that is directly attached to a heteroatom having a formal positive charge. The key difference between betaine and ylide is that the atoms containing the electrical charges are not always adjacent to each other in betaine, whereas these charged atoms are always adjacent to each other in ylides.

Reference:

1. “Betaine.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine.

Image Courtesy:

1. “Betaine” (CC BY-SA 3.0) via Commons Wikimedia
2. “Ph3P=CH2-ylid-phosphorane-resonance-2D” By Ben Mills – Own work (Public Domain) via Commons Wikimedia