A hydrogen bond is a weak interaction between a hydrogen attached to an electronegative atom and another electronegative atom. An example is between an NH group and a carbonyl:

The energy of the bond depends on the distance and angle between the three atoms, θ (e.g. N-H..O). You will explore the angular dependence in this experiment.

Use Excel to make a plot of energy versus θ for values from 90 to 270 degrees, using 20 degree increments. An easy way to set up the first column is to make the second degree cell equal to the first + 20, and then drag the cells down. To plot, highlight the data and use "Insert" and select scatter.

• What angle gives the lowest (most stable) energy?
• What is that energy?

Obtain the energy versus θ by entering a value for θ in this box:

θ =	deg
For the above value of θ, Calculate E
E =	kJ/mol