Description of the Organic Molecule 2-Hexyne

2-hexyne is the organic compound with the formula C2H5CH2CCCH3. It is an asymmetric alkyne. An asymmetric alkyne features varied groups attached to the two triple bonded carbons. Generally, alkynes are classified into terminal alkynes or internal alkynes. 2-hexyne is an internal alkyne in which the triple bond is not located at the end of the chain and there is no hydrogen attached to either of its triple-bonded carbons.

The structure of 2–hexyne is CH3-C ≡ C-C3H7

Each carbon atom involved in a triple bond is linearly hybridized, having two sp hybrid orbitals arranged about the nucleus at an angle of 180° to each other.

Synthesis

The synthesis of alkyne starts with acetylene, taking advantage of the fact that terminal hydrogen in an alkyne is acidic enough to be removed by a strong base like sodamide. This removal produces a carbanion that can serve as a nucleophile in an SN2 reaction with an alkyl halide, there by forming a carbon-carbon bond via an alkylation reaction. Starting with acetylene, a larger monosubstituted or disubstituted alkyne (asymmetrical or symmetrical) can be prepared using two separate SN2 steps:

General reaction

H-C ≡ C-H (Acetylene)–in the presence of NaNH2 and RX—→R-C ≡ C-H

(Monoalkylacetylene)—- in the presence of NaNH2 and RX—→R-C ≡ C-R’ (Dialkylacetylene)

Preparation of 2-Hexyne

H-C ≡ C-H (Acetylene)–in the presence of NaNH2—→[H-C ≡ C:]—in the presence of CH3-Br—→CH3-C ≡ C-H (Propyne) –in the presence of NaNH2— →[CH3-C ≡ C:]—in the presence of C3H7-Br—→CH3-C ≡ C-C3H7 (2-Hexyne)

Physical and chemical properties

Synonyms: Methyl propyl acetylene; METHYL-N-PROPYLACETYLENE; 1-Methyl-2-propylacetylene

Physical state: liquid

Color: colorless

Odor: hexane-like

Boiling point: 84-85 °C

Melting point: -90°C

Flash Point: -12 °F

Specific Gravity/Density: 0.731 g/mL at 25 °C

Molecular Formula: C6H10

Molecular Weight: 82.15 g/mol

Refractive index: n20/D 1.414(lit.)

Reactions of 2-hexyne

2-hexyne undergoes the following reactions to produce a variety of byproducts.

Addition

2-hexyne is an unsaturated compound therefore typically undergoes addition reactions. Because hexyne contains pi electrons, they are electron-rich and therefore electrophilic addition is their typical reaction. In addition to reactions, the reactants include hydrogen halides, halogens and water.

Hydrogenation

Catalytic Hydrogenation of hexyne to hexane results from the addition of two equivalents of hydrogen.

CH3-C ≡ C-C3H7 (2-Hexyne)–in the presence of platinum and 2H2—-→ CH3CH2CH2CH2CH2CH3 (hexane)

Oxidation

2-hexyne is readily oxidized by a variety of oxidizing agents like nitric acid, potassium permanganate. It results in complete cleavage at the triple bond with both resulting fragments being carboxylic acids.

CH3-C ≡ C-C3H7 (2-Hexyne) )–in the presence of KMnO4—-→ C4H9-COOH (Pentanoic acid) + COOH-OH (Carbonic acid) —→ CO2 +H2O

Potential health effects

2-hexyne is highly flammable. Potential side effects 2-hexyne is eye irritation, dermatitis or skin irritation and respiratory tract irritation. The toxicological properties of 2-hexyne is not been fully investigated. It can cause CNS depression if it is ingested in large amounts. Vapors sometimes cause suffocation or dizziness.

Potential Uses

Most organic polymers are electrical insulators; however, hexyne can be polymerized to a long chain as polyhexyne acts as an insulator. If the polyhexyne is doped with a trace of iodine it can conduct electricity, alteration of double and single bonds is the key to such conductivity. Recently, long chains of carbon joined by alternating triple and single bonds have been prepared called polyalkynes or molecular wires. Polyalkynes including polyhexyne have strength as carbon rods because of their rigidity and shown electrical conductivity properties. This property in future will show advancements in the field of Molecular electronics.