Reactions of Alcohol

Purpose:

To identify 4 different unmarked isomers of butanol from their physical and chemical properties, observed in various tests.

Hypothesis:

Structures 1 :

Solubility Rate of halogenation Rate of oxidizationHighest t-butanol t-butanol i-butanol

| s-butanol s-butanol n-butanol↓ i-butanol i-butanol s-butanol

Lowest n-butanol n-butanol t-butanol

Part 1:

In the isomers where more carbons are more evenly distributed and closer to the –OH group (e.g. t-butanol), the polarizing effect of the –OH is stronger whereas in structures such as n-butanol, where the –OH is at the end of a long chain, the polarizing effects of the -OH are weakened. As water dissolves polar molecules better, the order of the solubility will decrease more or less according to how evenly distributed the carbon atoms are from the –OH group. t-butanol will have the highest solubility, and n-butanol the lowest.

Part 2:

The reactivity of isomers of butanol with HCl (from the Lucas Reagent) is likely to be affected by solubility as the –OH group would have to be ionized, and then displaced by Cl- ions. For this exchange, the ions in butanol would have to be dissociated. Following this logic, the reactivity of each isomer will be proportionate to its solubility in water.

Part 3:1Diagrams from http://en.wikipedia.org/wiki/Butanol

n-butanol s-butanol i-butanol t-butanol

Sourabh Das 17/04/2023

KMnO4 is an oxidizing agent which will react with alcohol to increase the number of bonds between C and O. Primary alcohols (n-butanol, i-butanol) will be more reactive (and form carboxylic acids), then secondary alcohols (s-butanol) which will react to form aldehydes and ketones. Tertiary alcohols (t-butanol) cannot increase the number of C-O bonds as the carbon with the OH group is attached to 3 other carbons and the 4th bond is already with an O atom. This means tertiary alcohols will not oxidize at all.

Materials:

4 Samples of unique butanol isomers4 Test tubes4 Test tube stoppersTest tube rackPotassium permanganate

Lucas ReagentDistilled WaterGraduated CylinderWarm water bathSafety equipment

Procedure:

Part 1:

Distilled water (2mL)

Sourabh Das 17/04/2023

Part 2:

Part 3:

Observations:

WARM WATER BATH TO SPEED UP REACTION

1.0 M KMnO4 (2.0 mL)

WARM WATER BATH TO SPEED UP REACTION

DO NOT SHAKE

Lucas Reagent – conc. HCl + ZnCl (5mL)

Sourabh Das 17/04/2023

Isomer Before Test During After

A

ClearColourlessStrong odourLow viscosityBasic

12 visible layersUnstable emulsion visible

2Solution starts becoming cloudy at the bottom of t.t.

Cloudy at the bottomClear near the topPartial emulsification

3Slow reaction Turns reddish brown on heating

Slightly acidic

B

Colourless liquid on warm bathClearM.P. near S.A.T.PMild odourBasic

1Starts dissolving quickly Fully dissolved

Strong odour

2Some bubbling visible Emulsification visible

3NR N.R.

Basic

C

Low viscosityNo detectable odourBasic

1Partially dissolved

2NR NR

3NR Turns Brownish on heating

Partially coagulatesAcidic

D

ColourlessClearLow viscosityMild odourBasic

1Frothy on shaking Separated into layers

2NR 2distinct layers NR

3NR Turns Brownish on heating

Partially coagulatesAcidic

Discussion & Evaluation:

Sourabh Das 17/04/2023

Since each compound had the same molecular formula, their masses are identical. This means that the intermolecular forces are directly influenced by their structure with no variation due to molecular size.

The easiest isomer to identify was B as t-butanol as it had a very high M.P., dissolved in water quickly, and did not oxidize with KMnO4.

From the 3rd test, the most complete reaction in C & D shows that they are likely to be primary alcohols, while the slower reaction of A indicates a secondary alcohol. Also the partial emulsification during the Lucas test supports that A is a secondary alcohol. i.e. s-butanol

Between C and D, C is more soluble suggesting this is i-butanol. This leaves D as n-butanol.

This is the final analysis of which sample was which isomer:

A - s-butanol

B - t-butanol

C - i-butanol

D - n-butanol

There were many areas which could have been improved for more accurate results. The quantity of each solution and the reactant for each test were approximated. Measuring these may allow better comparison of how fast and how well each of the samples are reacting in each test.