Functional Group Identification of Organic Compounds via Wet Chemical Tests PDF

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Functional Group Identification of Organic Compounds via Wet Chemical Tests Lab Report...

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CHM 2211L September 2, 2021

Functional Group Identification of Organic Compounds via Wet Chemical Tests

Purpose: the purpose of this experiment is to be able to identify when functional groups are existing in different substances by using unknown chemicals and observing their reactions. While at the same time, one of the main intentions of this observation is to acquire knowledge on how to use quick chemical tests to determine if such groups (ketone, alkyl bromide, alkyl iodide, alcohol, alkene, amine, and carboxylic acid) are present.

Introduction: during this experiment an unknown was chosen to be blended with multiple different substances. Our group worked with Unknown E (colorless liquid) in particular and based on the test it was mixed with the amount to be added would vary. Therefore, we were able to determine the presence or absence of functional groups by observing the reactions and characteristics of each test.

Mechanisms: 1) The first test used was 2,4- Dinitrophenylhydrazine (2,4-DNP), which is used to detect the existence of ketones and/or aldehydes in a substance. Such presence can be determined by the formation of an orange, red or yellow precipitate. 2) The second test is the Alcoholic Silver Nitrate. The appearance of white solid indicates the presence of Alkyl and Allylic bromides, while yellow solid manifests Alkyl and Allylic iodides. 3) Chromic Anhydride test is used to react and show primary or secondary alcohols by creating a blue-green suspension (which is liquid with solid particles). 4) Then we used Bromine in Carbon Tetrachloride to determine the presence of an alkene. Bromine is a red/orange/brown substance but the disappearance of such color when mixed means it is positive and functional group is present.

5) Mixing Hydrochloric acid with the unknown will determine if amines are present, by dissolving and removing any layers or bubbles. 6) The last test used was Sodium hydroxide and the reaction expected to dictate if a functional group is present is very similar to the previous test. Test is positive if unknown substance dissolves and not layers or bubbles are constant.

Results (Data):

Test 2,4- Dinitrophenylhydrazine (2,4-DNP)

(+) or (-) +

Observations As soon as unknown was added it became orange-reddish and there was ppt. then it was heated and ppt disappeared. After 5 minutes in hot water bath the

Alcoholic AgNO3

-

solution liquified. Contained Ketone. After adding the unknown nothing happened, we got a clear liquid. When warmed in hot water it became bubbly but after taken out it went back to clear liquid. No Alkyl

Chromic Anhydride

-

bromide nor Alkyl iodide. Once the chromic anhydride was added it ppt and turned into a yellow-orange substance, it was also warm. As per our observations it did not contain Alcohol since the color

Bromine in Carbon Tetrachloride

-

wasn’t the expected one. When first drop was added there were fumes present and liquid was clear. After adding the second drop it turned

Solubility in HCl Solubility in NaOH

+

light yellow and stayed the same after third drop. After adding 5% HCl it turned cloudy and had a jelly form.

-

once it was well mixed the jelly substance disappeared. Once NaOH was added cloudiness and bubbles were present. After mixing for a few seconds it all disappeared but a layer was formed. Solution had a colorless liquid form. No Carboxylic acid was present.

Conclusion:

Since the aim of this experiment was to teach how to identify functional groups we can say it was a successful investigation and even though not all the results were positive it allowed us to determine when a reaction showed the presence of a group or not. Based on the observations and the characteristics of the reactions, we could say that the chosen unknown contained Ketone and Amines....