Structure and Bonding: The Carbon-Nitrogen Bond

The carbon-nitrogen bond is very important in many biological molecules.

Measure and record the carbon-nitrogen bond distances (right click, select, mouse click action, then click on distance) in the following molecules given below.  

methylamine                    methylimine                        hydrogen cyanide

single bond                     double bond                     triple bond   

type of bond bond order occurs in bond energy (kJ/mole) bond length (pm)
single 1 amines 305  
double 2 imines 615  
triple 3 nitriles 887  

When the H of HCN is replaced with a carbon chain, R, the resulting group is called a nitrile, RCN.

How does the bond length vary with bond order?

How does the bond energy vary with bond length? 

What is this telling you about the strength of a bond?  Explain.

The structure of methanamide is given below.  The C-N bond should be a single bond.  Measure its distance and decide if this is correct.

How would you characterize the bond order in methanamide?

Here is the structure of a chain of amino acids, as they would occur in a sheet protein.  Measure the distances of the C-N bonds.  To zoom in: press and hold the shift key, click, and move the mouse

Notice that there are two different carbon-nitrogen bonds in the chain.  How would you characterize them?

Can bond rotation occur around a bond with a bond order greater than one?

Does a chain of amino acids have the same rotation capability as a long chain hydrocarbon, C12H26?

The structure below is another geometry that the chain of amino acids can take.  How would you describe it?

To help see the shape - right click on the image, select display, and click on backbone.  You may want to go back to the first chain structure and look at the backbone there.

The chains of amino acids in proteins can be sheets or the alpha helix as just seem above.

View the two proteins below and decide if they are helix or sheet proteins.  You may want to change the display to cartoon to help.

HIV protease                          hemoglobin

If you go to color and select chain, the number of colors in the molecule tells you the number of chains or subunits in the protein.

How many subunits in the  HIV protease?             in hemoglobin? 

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