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Lactic acid and alanine are both important chemicals in living systems - VCE - SSCE Chemistry - Question 2 - 2003 - Paper 1
Question 2
Lactic acid and alanine are both important chemicals in living systems. Their structures are 1. Give the name of the functional group common to both compounds. ... show full transcript
Worked Solution & Example Answer:Lactic acid and alanine are both important chemicals in living systems - VCE - SSCE Chemistry - Question 2 - 2003 - Paper 1
Step 1
Step 2
Why is alanine classified as an amino acid but lactic acid is not?
Answer
Alanine is classified as an amino acid because it contains both an amino group (-NH₂) and a carboxyl group (-COOH), making it capable of participating in peptide bond formation. In contrast, lactic acid lacks an amino group, therefore it does not meet the criteria to be classified as an amino acid.
Step 3
In the boxes below, draw structures of two different possible organic molecules formed by a condensation reaction between lactic acid and alanine.
Answer
Two organic molecules can form from the condensation reaction between lactic acid and alanine. The first structure is a peptide, where an amine from alanine reacts with the carboxylic acid from lactic acid. The second structure can be an ester, formed by the condensation of the hydroxyl group of lactic acid and the carboxylic group from alanine. Note that the actual drawings are to be done in the provided boxes.
Step 4
For one of the structures given in part c.,
Answer
i. Circle the new functional group formed: The new functional group will depend on the structure chosen (either a peptide bond or an ester bond).
ii. Name the functional group that you have circled: If you circled the amide bond, then it is classified as an amide functional group (-CONH-). If you circled the ester bond, it is classified as an ester functional group (-COO-).