Triple Bond in Alkynes, Introduction, Uses of Alkynes, Questions (For CBSE, ICSE, IAS, NET, NRA 2022)

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Triple Bond in Alkynes
  • When three pairs of electrons are shared between two carbon atoms, a triple bond is formed between the two carbon atoms.
  • The triple bonded carbon atoms of acetylene are hybridized. Sigma bond between the atoms of carbon is obtained by a head – on overlapping of the two hybridized orbitals.

Introduction to Alkynes

  • Quantum mechanics helps us to study the structure of different molecules found in nature. The concept of chemical bonding in combination with quantum mechanics has revealed numerous information about various organic and inorganic compounds that are essential for life.
  • Acetylene is the simplest member of the alkyne family. Alkynes are unsaturated hydrocarbons in which a carbon-carbon triple bond exists between the two carbon atoms.

What is a Triple Bond?

A Triple Bond

When three pairs of electrons are shared between two carbon atoms, a triple bond is formed between the two carbon atoms. The distinguishing features of alkynes from the other hydrocarbons are the triple bond which exists between the carbon atoms.

A Triple Bond
  • The triple bonded carbon atoms of acetylene are hybridized. Sigma bond between the atoms of carbon is obtained by a head-on overlapping of the two hybridized sp orbitals. The leftover orbitals of the carbon atoms overlap with each other along the internuclear axis in the 1s orbital of each hydrogen atom which results in the formation of one C-H sigma bond and 2 weaker pi bonds. These bonds are formed due to orbital overlapping. Each carbon atom uses only one of its three p-orbitals.
  • 2 remaining p orbitals are occupied by a single electron. As it is same with the other carbon atom, this permits the pairing of electrons which results in the formation of 2 pi bonds. The carbon-carbon triple bond is made stronger by the presence of one sigma bond.
  • Acetylene is a linear molecule with carbon-carbon distance of . The distance in acetylene is shorter than alkenes due to the fact that sp hybridized carbon has more s character than the sp2 hybridized carbon.

Uses of Alkynes

The most common form of alkynes Ethyne is used in preparing many other compounds. some of these uses are as follows:

  • The most common use of Ethyne is for making organic compounds like ethanol, ethanoic acid, acrylic acid, etc.
  • It is also used for making polymers and its beginning materials. for instance, vinyl chloride is used as the starting material for PVC and chloroprene is used for synthetic rubber neoprene.
  • Ethyne is used for preparing many organic solvents.
  • Alkynes are commonly used to artificially ripe fruits.
Uses of Alkynes

Questions

Does Alkyne Have a Triple Bond?

Answer:

  • Alkynes are hydrocarbons which contain carbon-carbon triple bonds. Their general formula is for molecules with one triple bond (and no rings) .
  • Triple-bonded carbons are , and have linear shapes, with the bonded atoms at angles of to each other.

Which Alkyne is Most Acidic?

Answer:

  • The acidity of a terminal alkyne is due to the high level of s character in the sp hybrid orbital, which bonds with the s orbital of the hydrogen atom to form a single covalent bond.
  • The high level of s character in an hybridized carbon causes the overlap region of the σ bond to shift much closer to the carbon atom.

What is a Triple Bond Called?

Answer:

  • A triple bond in chemistry is a chemical bond between two atoms involving six bonding electrons instead of the usual two in a covalent single bond.
  • The most common triple bond, that between two carbon atoms, can be found in alkynes. Other functional groups containing a triple bond are cyanides and isocyanides.

How Do You Name Alkynes with Two Triple Bonds?

Answer:

  • When there are two triple bonds in the molecule, find the longest carbon chain including both the triple bonds.
  • Number the longest chain starting at the end closest to the triple bond that appears first. The suffix that would be used to name this molecule would be – diyne.

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