The triple covalent bonds are chemical bonds in which two atoms share three pairs of electrons. In other words, they are covalent bonds formed by a total of six valence electrons that revolve around two atoms.
There are many chemical compounds that contain triple bonds. For example, organic compounds such as alkynes contain CC triple covalent bonds. Nitriles are also characterized by having a group containing a carbon linked to a nitrogen through a triple CN covalent bond. Other inorganic compounds, such as molecular nitrogen in air, also contain triple covalent bonds.
Having 6 electrons spinning around two nuclei gives triple bonds many unique characteristics. Both the shape of the molecules that contain them, and the chemical reactions in which they can participate are different from those of double or single bonds.
Characteristics of the triple covalent bond
They are made up of 6 electrons
These bonds are made up of 6 electrons and are formed when each of the two atoms involved shares three of its unpaired electrons with the other. This is the reason why they are called triple bonds, since they have triple the number of electrons of the single covalent bond.
They have one sigma bond (σ) and two pi bonds (π)
Similar to double bonds, triple bonds are also made up of a sigma bond that passes through the center of the line joining the two bonded atoms. However, unlike double bonds that have one, triple bonds have two pi bonds in addition to the sigma bond.
They almost always form linear compounds
When two carbon atoms form a triple bond, they each still have a chance to form an additional single bond with another atom (since carbon can form 4 bonds in total).
In these cases, both the two carbons and the other two atoms attached to them will form a straight line. This shape that the molecule takes is called linear geometry.
They are the strongest covalent bonds
When comparing the triple bonds between two atoms with the double and single bonds between those same atoms, it is observed that the triple bonds are always stronger than the other types of covalent bond. This means that it is more difficult to break a triple bond than a double or single one.
This is because, in addition to having to break the sigma bond (which is also present in both single and double bonds), you have to break not one (as in double bonds) but two additional pi bonds.
By the very fact of being stronger bonds, triple bonds manage to bring the nuclei of atoms closer to each other, which makes triple bonds shorter than double and single bonds.
They represent two unsaturations
Each carbon that has a triple bond will have only one additional bond with another atom. This means that said carbon would be linked only to two atoms, instead of four, so it has less hydrogens than it could have if it only formed single bonds.
This is called unsaturation, and triple-bonded compounds have two unsaturations, since each of the two carbons would fit 2 additional hydrogens, were it not for the triple bond.
They are rigid links
Like double bonds, triple bonds are stiff and difficult to bend or twist. This is due to both the higher bond force and the shorter length.
They can act as bases
Some triple bonded compounds can use the pi electrons from that bond to bond or accept H + ions , thus acting as bases.
They can be hydrogenated to give double or single bonds
The unsaturations of the triple bond can be removed by breaking the pi bonds and adding hydrogens to the two carbons. This is called hydrogenation. If only one hydrogen molecule is added to a triple bond, it will become a double bond. If two hydrogen molecules are added, it will become a single bond.
Examples of triple covalent bonds
Nitrogen molecule (N 2 )
The nitrogen molecule contains a triple covalent bond between the two nitrogen atoms. Each atom shares its three unpaired valence electrons with the other, and each new pair of electrons forms either the sigma bond or one of the two pi bonds that the molecule possesses.
In this case, both the two nitrogen atoms and the unshared pairs of electrons each possess are located along a straight line.
Propyne (an alkyne of the formula C 3 H 4 )
Tip is the second simplest alkyne that exists. This compound is made up of a chain of three carbons, two of which are linked by means of a triple covalent bond.
Here it can also be seen that the three carbons and the last hydrogen atom (the one on the right) form a straight line. In the model it can also be seen that the single CC bond is longer than the triple CC bond.
Carbon monoxide (CO)
Carbon monoxide is a toxic inorganic gas that has a negative carbon atom and a positive oxygen linked by a triple covalent bond. In this case, it is a polar bond, due to the difference in electronegativities between carbon and oxygen.