Properties of Alcohol

Topics: Alcohol, Oxygen, Hydrogen Pages: 5 (709 words) Published: April 11, 2014


Experiment 5:
Properties of Alcohols

Purpose
The purpose of this experiment was to understand the comparative solubility of alcohols, as well as perform qualitative tests for the identification of alcohols. Theory
Part I relies on the fact that different alcohols have different solubility in either water or hexane depending on both the number of hydroxide functional groups and the number of carbons in the molecule. The shorter the hydrocarbon chain, the more polar the molecule is. This polarity makes shorter alcohol chains more soluble in water, but less soluble in organic solvents such as hexane. The opposite is also true. The longer the hydrocarbon chain, the less influence the oxygen atom’s electronegativity has on the molecule’s overall polarity. This decreasing molecular polarity leads to decreased solubility in water, but increasing solubility in hexane and other organic solvents. Part II relies on the fact that that primary, secondary, and tertiary alcohols, as well as phenols have different oxidation and reduction potentials, and react differently with other molecules. Primary alcohols can be oxidized into aldehydes, and subsequently into carboxylic acids. Meanwhile, secondary alcohols can only be oxidized into ketones, and tertiary alcohols cannot be oxidized at all because they lack bonded hydrogen atoms to be substituted. Exploiting these properties by performing four different qualitative tests will enable distinction between the different types of alcohol. Results

Part I-Solubility

NS=Insoluble

XXX=Completely Soluble XX=Partially soluble X= Sparingly soluble
 
Methanol
Ethanol
Butanol
Hexanol
Octanol
Phenol
Water
XXX
XXX
X
NS
NS
XXX
Hexane
XX
XXX
XXX
XXX
XXX
NS/X

Part-II

Test Tube #
1
2
3
4
5
Test
1-Butanol
2-Propanol
2-Methyl-2-Propanol
Resorcinol
Water
Lucas
Remained Colorless
No rxn immediately, solt'n turned cloudy white after 5 mins heat Immediately turned solt'n cloudy white
light brown color change
Remained Colorless
 

Chromic Acid
Dark blue-green precipitate
Light blue-green precipitate
Yellow-orange color
Dark brown color change
Yellow-orange color
 

 
 

Iodoform
Slight yellow color change
Light yellow precipitate
Slight yellow color change
Fine, light yellow precipitate
Slight yellow color change
 

 

Ferric Chloride
Yellow
Light yellow
Light yellow
Dark purple color change
Light yellow
 
 
 
 

Data Analysis
Conclusion
References
Manual Questions:
1. Methanol and ethanol are soluble in water because of the presence of OH group which is capable of dipole -dipole interactions and hydrogen bonding. The OH group plays a major role in interaction with water. As the carbon chain increases, the compound will behave more like an alkane and thus it will be less soluble in water such as butanol which is only sparingly soluble in water. Hexanol and Octanol were not soluble due to their large carbon chain as the compound as a whole is more non polar than polar. Phenols are soluble in water because of the OH group and they are generally form strong hydrogen bonds. As for the solubility in hexane, methanol and ethanol aren’t soluble or only slightly soluble in hexane due to them being polar and hexane being non polar. But when the experiment was done in the lab, hexane and ethanol turned out to be soluble. It might be due to unequal quantities of solutions being used or it might have not been observed properly. For butanol,hexanol and octanol, the non-polarity increases with increase in carbon chain, so they are completely soluble in hexane which is non-polar as ‘like dissolves like’. Phenol doesn’t dissolve in hexane due to it being polar (OH group) and hexane being non-polar.

2. 1-Hexanol

2-methyl-2-hexanol

As 1-Hexanol is a primary alcohol and 2-methyl-2-hexanol is a tertiary...

References: Manual Questions:
1. Methanol and ethanol are soluble in water because of the presence of OH group which is capable of dipole -dipole interactions and hydrogen bonding. The OH group plays a major role in interaction with water. As the carbon chain increases, the compound will behave more like an alkane and thus it will be less soluble in water such as butanol which is only sparingly soluble in water. Hexanol and Octanol were not soluble due to their large carbon chain as the compound as a whole is more non polar than polar. Phenols are soluble in water because of the OH group and they are generally form strong hydrogen bonds. As for the solubility in hexane, methanol and ethanol aren’t soluble or only slightly soluble in hexane due to them being polar and hexane being non polar. But when the experiment was done in the lab, hexane and ethanol turned out to be soluble. It might be due to unequal quantities of solutions being used or it might have not been observed properly. For butanol,hexanol and octanol, the non-polarity increases with increase in carbon chain, so they are completely soluble in hexane which is non-polar as ‘like dissolves like’. Phenol doesn’t dissolve in hexane due to it being polar (OH group) and hexane being non-polar.
2. 1-Hexanol
2-methyl-2-hexanol
As 1-Hexanol is a primary alcohol and 2-methyl-2-hexanol is a tertiary alcohol, Lucas Test and the Chromic acid test could be used to distinguish between primary, secondary and tertiary alcohols. 1-Hexanol added to the lucas reagent gives no reaction and 2-methyl-2-hexanol when added to lucas reagent reacts rapidly to give an insoluble white layer. In the chromic acid test, primary alcohols like 1-hexanol gets oxidized to aldehydes and then to carboxylic acids while tertiary alcohols like 2-methyl-2-hexanol are not oxidized.
3. The carbon in primary alcohol has two hydrogen atoms, so two oxidation products are possible which are an acid and an aldehyde. In secondary alcohol, there is only one hydrogen atom so only one oxidation product is possible. As tertiary alcohols have no hydrogen, no oxidation takes place thus no reaction takes place.
Primary alcohol:
Secondary alcohol:
Tertiary alcohol:
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