Alcohols and Hydrochloric Acid: The solubility and reactivity of n- and t-Pentanol

chemical equation asking the question, 'What happens when n- and t- pentanol are mixed with water and aqueous hydrochloric acid'

During this activity students will investigate the solubility of n- and t-pentanol in water and in aqueous hydrochloric acid. Students will also investigate the reactivity of t-pentanol with hydrochloric acid.

Solubility Tests

First, n-pentanol and t-pentanol are added to four test tubes.

Note: The labels on the n-pentanol test tubes were erroneously reversed; that is, the aqueous HCl and water test labels should be switched.

Before the water is added, make a prediction about whether you expect the alcohols to dissolve.

Before the aqueous hydrochloric acid is added, make a prediction about whether you expect the alcohols to dissolve.

The Reaction of t-Pentanol with Hydrochloric Acid

a chemical eauation showing the production of an insoluble silver salt and an ethyl ether from a generic chlorine or bromoine containing halohydrocarbon reacting with ethanol in the presence of silver nitrate.

t-Pentanol is added to a 15-mL centrifuge tube and the mass of the added t-pentanol is determined by comparing the mass of the empty container to the mass of the filled centrifuge tube.

Hydrochloric acid is added to a centrifuge tube that contains t-pentanol. The centrifuge tube is shaken for 30 seconds, vented and schaken for an additional 3 minutes.
After the mixture is shaken for three minutes, the organic and aqueous layers are separated. Confirming the identification of the aqueous and organic layers can be beneficial. Do so by adding a small amount of water to the presumed aqueous layer.

TIP: The layers can be very difficult to see. Use a high contrast background to find the junction between the layers. Transferring the solution to a more transparent container may be helpful. Note in the video that the contrast between the dark line in the hood and the white background is the only thing that makes the transition from one layer to the next visible.

Wash the product with 2 mL of water; that is, add 2 mL of water to the organic layer, shake, separate the layers, and discard the aqueous layer.

TIP: The product, t-pentyl chloride, reacts with water, so this step should be done quickly.

Add 2 mL of an aqueous 5% sodium bicarbonate solution to the organic layer. Shake, separate the layers, and discard the aqueous layer.

TIP: The product, t-pentyl chloride, reacts with water, so this step should be done quickly.

Several scoops of anhydrous sodium sulfate are added to dry the organic layer.

TIP: The sodium sulfate should roll freely in the organic layer. If all of the sodium sulfate clumps together, add another scoop.

The t-pentyl chloride can be separated from any t-pentanol that might remain by distilling the t-pentyl chloride.

Results

t-Pentyl chloride was collected in a tared 3-mL conical vial. Infra-red spectral data for the starting material and the product were collected using a diamond crystal, attenuated total reflectance module on an Cary 630 FT-IR.
a photograph of the empty 3-mL conical vial on an analytical balance. The mass of the empty vials reads as 18.4364 g.
The mass of the empty 3-mL conical vial. 		a photograph of a 3-mL vial containing the t-pentyl chloride product. The mass of the combination reads as 18.5560 g
The mass of the 3-mL conical vial and the t-pentyl chloride product.
IR spectrum of t-pentanol where a broad OH peak is clearly visible in the infra-red spectrum.
An infra-red spectrum of t-pentanol. Note the presence of the broad OH peak near 3450 cm-1. 		IR spectrum of t-petnyl chloride where the broad OH peak is no longer present in the spectrum.
An infra-red spectrum of t-pentyl chloride. Note the absence of a broad OH peak around 3450 cm-1. Note the similarities between the three peaks in the two spectra at just below 3000 cm-1. This is the "C-H stretching region", and as the C-H framework of the molecule hasn't changed, one might expect that region of the IR spectra of the molecules to be similar.