3-Hexyne is the organic compound

Organic compound

An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...

 with the formula C₂H₅CCC₂H₅. This colorless liquid is the most common of the three isomeric hexynes. Together with 2-butyne and diphenylacetylene

Diphenylacetylene

Diphenylacetylene is the chemical compound C6H5C≡CC6H5. The molecule consists of phenyl groups attached to both ends of an alkyne. It is a colorless crystalline material that is widely used as a building block in organic and as a ligand in organometallic chemistry.-Preparation:Several...

, it serves as a reference acetylenic

Acetylene

Acetylene is the chemical compound with the formula C2H2. It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is unstable in pure form and thus is usually handled as a solution.As an alkyne, acetylene is unsaturated because...

 ligand

Ligand

In coordination chemistry, a ligand is an ion or molecule that binds to a central metal atom to form a coordination complex. The bonding between metal and ligand generally involves formal donation of one or more of the ligand's electron pairs. The nature of metal-ligand bonding can range from...

 in organometallic chemistry

Organometallic chemistry

Organometallic chemistry is the study of chemical compounds containing bonds between carbon and a metal. Since many compounds without such bonds are chemically similar, an alternative may be compounds containing metal-element bonds of a largely covalent character...

. 3-Hexyne is useful because the ¹H NMR

NMR spectroscopy

Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy, is a research technique that exploits the magnetic properties of certain atomic nuclei to determine physical and chemical properties of atoms or the molecules in which they are contained...

 signals for the methylene

Methylene

Methylene is a chemical species in which a carbon atom is bonded to two hydrogen atoms. Three different possibilities present themselves:* the -CH2- substituent group: e.g., dichloromethane ....

 groups convey stereochemical information in its octahedral complexes

Octahedral molecular geometry

In chemistry, octahedral molecular geometry describes the shape of compounds where in six atoms or groups of atoms or ligands are symmetrically arranged around a central atom, defining the vertices of an octahedron...

.

Spectral characteristics

In a proton NMR spectroscopy result, 3-hexyne produces a triplet of integrated area 6H at a chemical shift of approximately 1.0 ppm and a quartet of integrated area 4H at approximately 2.2 ppm. The less deshielded triplet corresponds to the terminal methyl hydrogen atoms that experience spin-spin splitting from the adjacent methylene hydrogen atoms. The quartet corresponds to the more deshielded methylene hydrogen atoms that are spin-spin split by the adjacent methyl hydrogen atoms. The methylene hydrogens don't form a complex multiplet because the internal alkyne function that is adjacent to them does not contain any bonded hydrogen atoms with which they can interact. The overall symmetry of the molecule causes both methylene groups to contain hydrogen atoms in exactly the same electronic environment. The same logic follows to explain the identical spectroscopic results provided by the hydrogen atoms on all methyl groups.