# Question #9e047

Jun 10, 2017
1. Via intermolecular forces
2. Hydrogen bonding

#### Explanation:

Take a look at the wonderful image just below.

This image shows you the nitrogenous bases that are purines and pyrimidines. The $\textcolor{m a \ge n t a}{\text{purines}}$ are $\textcolor{m a \ge n t a}{\text{Adenine (A)}}$ and $\textcolor{m a \ge n t a}{\text{Guanine (G)}}$. The $\textcolor{b l u e}{\text{pyrimidines}}$ are $\textcolor{b l u e}{\text{Thymine (T)}}$ and $\textcolor{b l u e}{\text{Cytosine (C)}}$.

Purines base pair with pyrimidines. This means A pairs with T and G pairs with C. They pair by forming Hydrogen bonds, a type of intermolecular bond and one of the strongest types of intermolecular bonds out there. This type of bond is different from an intramolecular bond which exists between atoms within the molecule itself.

Hydrogen bonds only occur between $\textcolor{red}{\text{F, O, or N}}$. These atoms are very electronegative meaning they are hungry for electrons and will pull all the electron density towards themselves. This gives them a partial negative charge $\left(\delta -\right)$. Hydrogen, on the other hand, is not so electronegative and instead will bear a partial positive charge $\left(\delta +\right)$. When you get a partial negative charge next to a partial positive charge, the hydrogen bond will exist, assuming other conditions are met.