As an organic chemistry student studying substitution and elimination reactions, one of the topics that you will face on a regular basis is the classification of solvents. In this article I will show you how to recognize the different solvent types to that you can comfortably apply them to your SN1 SNE E1 E2 reactions Solvents fall into 3 main categories. Polar Protic Solvents, Polar Aprotic Solvents, Non-Polar Solvents
A polar solvent, as the name implies, has 2 poles. A partially positive and a partially negative pole. This occurs when the solvent molecule is made up of atoms that while covalently bound, are not sharing the electrons equally among the bonding atoms. The more electronegative atom will pull the electrons towards itself resulting in a slightly negative charge or 'pole', while the less electronegative atom winds up with a partially positive charge or 'pole'
The word protic, in polar protic solvents, comes from the word proton, which is simply the positive nucleus of a hydrogen atom. When hydrogen is bound to a very electronegative atoms like N, O or F, these atoms form polar covalent bonds that are so extreme, to the point where not only is hydrogen partially positive, but its entire nucleus is exposed. Since the nucleus of hydrogen contains one proton, the exposed proton makes the solvent protic. If another highly electronegative atom like N, O or F comes across this protic hydrogen, it will attempt to make a bond, called a hydrogen bond. Examples of polar protic solvents include water and ammonia
Polar aprotic solvents tend to be the most confusing. While the solvent molecules do have partial charges or polarity, they are incapable of hydrogen bonding. this is because the polarity typically does not occur between a hydrogen and nitrogen, or hydrogen and oxygen atom.
A common example is the solvent acetone, also known as propanone. This condensed molecular formula for the polar aprotic acetone is CH3C=OCH3. Notice that the pi bond (double bond) between carbon and oxygen will result in a partial positive pole on the carbon and a partial negative pole on the oxygen. However, there are no H atoms on the oxygen. Instead the only H atoms on this molecule are found on carbon. This bond is non-polar covalent and will not allow the solvent to hydrogen bond
A polar solvent, as the name implies, has 2 poles. A partially positive and a partially negative pole. This occurs when the solvent molecule is made up of atoms that while covalently bound, are not sharing the electrons equally among the bonding atoms. The more electronegative atom will pull the electrons towards itself resulting in a slightly negative charge or 'pole', while the less electronegative atom winds up with a partially positive charge or 'pole'
The word protic, in polar protic solvents, comes from the word proton, which is simply the positive nucleus of a hydrogen atom. When hydrogen is bound to a very electronegative atoms like N, O or F, these atoms form polar covalent bonds that are so extreme, to the point where not only is hydrogen partially positive, but its entire nucleus is exposed. Since the nucleus of hydrogen contains one proton, the exposed proton makes the solvent protic. If another highly electronegative atom like N, O or F comes across this protic hydrogen, it will attempt to make a bond, called a hydrogen bond. Examples of polar protic solvents include water and ammonia
Polar aprotic solvents tend to be the most confusing. While the solvent molecules do have partial charges or polarity, they are incapable of hydrogen bonding. this is because the polarity typically does not occur between a hydrogen and nitrogen, or hydrogen and oxygen atom.
A common example is the solvent acetone, also known as propanone. This condensed molecular formula for the polar aprotic acetone is CH3C=OCH3. Notice that the pi bond (double bond) between carbon and oxygen will result in a partial positive pole on the carbon and a partial negative pole on the oxygen. However, there are no H atoms on the oxygen. Instead the only H atoms on this molecule are found on carbon. This bond is non-polar covalent and will not allow the solvent to hydrogen bond
About the Author:
Now see how protic and aprotic solvents relate to substitution and elimination reactions by watching my YouTube video on Polar Protic, Aprotic, Non-Polar Solvents