A compound with molecular mass 180 is acylated with CH 3COCl to get a compound with molecular mass 390. The number of amino groups present per molecule of the former compound is: (1) 5 (2) 4 (3) 6 (4) 2

To solve this problem, we need to analyze the molecular mass changes that occur during the acylation of the compound with CH3COCl (acetyl chloride). The key here is to understand how acylation affects the molecular mass and how many amino groups are present in the original compound.

Understanding Acylation

Acylation is a chemical reaction where an acyl group (in this case, the acetyl group from CH3COCl) is introduced into a molecule. When a compound containing amino groups is acylated, each amino group can react with one molecule of acetyl chloride, leading to an increase in the molecular mass of the compound.

Calculating the Mass Increase

Let's break down the information we have:

• The original compound has a molecular mass of 180 g/mol.
• After acylation, the new compound has a molecular mass of 390 g/mol.

The increase in molecular mass due to acylation can be calculated as follows:

Increase in mass = New mass - Original mass

Increase in mass = 390 g/mol - 180 g/mol = 210 g/mol.

Mass Contribution from Acetylation

Each acetyl group (CH3CO-) contributes a mass of approximately 42 g/mol (12 for carbon, 1 for hydrogen, and 16 for oxygen). Therefore, if we denote the number of amino groups in the original compound as 'n', the total mass increase from acylation can be expressed as:

Mass increase = n × 42 g/mol

Setting the two expressions for mass increase equal gives us:

n × 42 g/mol = 210 g/mol

Solving for the Number of Amino Groups

Now, we can solve for 'n':

n = 210 g/mol / 42 g/mol = 5

Final Answer

Thus, the original compound contains 5 amino groups per molecule. Therefore, the correct answer is (1) 5.

This analysis shows how acylation can be quantitatively assessed by examining the changes in molecular mass, allowing us to deduce the number of functional groups present in the original compound. If you have any further questions about this process or related topics, feel free to ask!