# Question #16a6b

Mar 21, 2014

There are 47 sigma bonds in a molecule of citalopram.

Here is an image of a citalopram molecule:

A single bond consists of one sigma bond. A double bond consists of one sigma and one pi bond. A triple bond consists of one sigma bond and two pi bonds.

Remember that in line structures there is a C atom at each angle and at the end of each line. Each C atom must have four bonds. Any missing bonds are C-H bonds.

Thus, in the benzene rings, the C atoms with only 3 bonds shown also have an unshown C-H bond. The zigzag line at the left contains three CH₂ groups. The 5-membered ring contains a CH₂ group. The two lines coming from the N atom represent CH₃ groups.

Let’s start counting from the lower left corner of the molecule.
1 N-C + 1 C-C = 2 σ bonds

The 6-membered ring + the 5-membered ring = 8 C-C bonds + 2 C-O bonds + 5 C-H bonds = 15 σ bonds.

The top 6-membered ring = 6 C-C + 1 C-F + 4 C-H + 1 C-C to the 5-membered ring = 12 σ bonds.

The side-chain at the left = 3 C-C + 3 C-N + 12 C-H = 18 σ bonds

TOTAL = 2 + 15 + 12 + 18 = 47 σ bonds