Question

How will you distinguish between chloroethane and vinyl chloride?

Short answer

Differentiate chloroethane and vinyl chloride by boiling point, IR spectroscopy (C=C stretch for vinyl), or bromine water test (vinyl reacts).

Step-by-step solution

Introduction to Chemical Structure

Chloroethane (eC2H5Cl) is an alkane with a single chlorine atom attached to an ethyl group. Vinyl chloride (eC2H3Cl), on the other hand, has a chlorine atom attached to a carbon-carbon double bond (alkene). The difference in saturation (single vs. double bond) influences their reactivity and boiling points.

Physical Properties

Examine the boiling points of both compounds. Chloroethane has a boiling point close to 12-13°C, while vinyl chloride boils at -13.4°C. This considerable difference can be used to distinguish them via simple distillation or boiling point determination tests.

Infrared (IR) Spectroscopy

Conduct IR spectroscopy. Vinyl chloride, being an alkene, will show distinct C=C stretching vibrations around 1650 cm^{-1}, which will not be present in chloroethane. Additionally, the C-Cl stretch will appear in both spectra around 700-800 cm^{-1} but will not differentiate them.

Reactivity with Bromine Water

Test each compound with bromine water. Chloroethane, being saturated, will not react or decolorize the orange color of bromine water. Vinyl chloride, with its double bond, will react and decolorize the bromine water, signaling the presence of an alkene.

Key concepts

Alkane vs Alkene

When it comes to organic chemistry, distinguishing between alkanes and alkenes is key. Alkanes, like chloroethane, are fully saturated hydrocarbons which means they contain single bonds only. This results in them being less reactive compared to other organic compounds. On the contrary, alkenes such as vinyl chloride contain at least one carbon-carbon double bond. This unsaturation introduces additional reactivity, making them more prone to participate in reactions. The presence of the double bond in alkenes is a significant identifying feature that will influence their behavior in various tests and reactions.
Understanding this basic difference helps chemists predict how each compound will react, and allows them to use targeted tests to differentiate between an alkane and an alkene.

Boiling Point Determination

Boiling point is one of the key physical properties used to identify and distinguish substances. In the context of chloroethane and vinyl chloride, boiling point determination becomes particularly useful. Chloroethane boils at approximately 12-13°C. In contrast, vinyl chloride has a significantly lower boiling point of -13.4°C. This substantial difference is due to the varying level of intermolecular forces present in each compound.
By conducting a simple boiling point determination test, one can easily conclude which compound is present. This test involves heating the substance and measuring the temperature at which it transitions from liquid to gas. Such measurable differences provide a practical tool for distinguishing between these two similar-looking compounds.

Infrared Spectroscopy

Infrared (IR) spectroscopy is an invaluable tool for distinguishing between different organic compounds based on their molecular vibrations. This technique helps identify functional groups by observing the absorption of specific wavelengths. Chloroethane and vinyl chloride can be successfully differentiated using IR spectroscopy.

• Vinyl chloride, as an alkene, will exhibit a C=C stretching vibration, typically seen around 1650 cm^{-1}. This double bond signature is absent in chloroethane, making it a distinguishing feature.
• Both compounds will present C-Cl stretching vibrations in the 700-800 cm^{-1} range, which won't aid in differentiation.

By focusing on the presence of the C=C bond vibration, one can reliably distinguish vinyl chloride from chloroethane through their unique IR spectra.

Bromine Water Test

A practical chemical test to differentiate alkanes from alkenes is the bromine water test. This test exploits the differing chemical reactivity due to the absence or presence of a double bond. Bromine water is an orange solution due to bromine, and it can indicate reactions with unsaturations.

• In the bromine water test, chloroethane, a saturated alkane, will not react and thus retain the orange color of the bromine water.
• Vinyl chloride contains a C=C double bond. Upon exposure to bromine water, it will react and prompt the solution to become colorless as the bromine adds across the double bond.

Thus, through a simple qualitative test like the bromine water test, you can effectively distinguish between these two compounds by observing the change or lack thereof in the solution's color.