Synthesis of p-bromoaniline Result section From Step 1: Weight of 4-bromoacetanilide is 2.5g. Properties: C HBrNO, Molecular weight: 214.06g/mol, Melting Point: 168°C Please note that the ratio of acetanilide to 4-bromoacetanilide is 1:1. Calculate the actual yield?
The Correct Answer and Explanation is:
Actual Yield Calculation and Explanation – Synthesis of p-Bromoaniline (Step 1: 4-bromoacetanilide)
Given Data:
- Product: 4-bromoacetanilide
- Weight of product (actual yield): 2.5 g
- Molecular formula: C₈H₈BrNO
- Molecular weight: 214.06 g/mol
- Starting material: acetanilide
- Molar ratio (acetanilide : 4-bromoacetanilide) = 1:1
Step 1: Calculate Moles of 4-Bromoacetanilide
Moles=MassMolecular Weight=2.5 g214.06 g/mol≈0.01169 mol\text{Moles} = \frac{\text{Mass}}{\text{Molecular Weight}} = \frac{2.5\,g}{214.06\,g/mol} \approx 0.01169\,mol
So, actual yield = 0.01169 mol of 4-bromoacetanilide.
Step 2: Determine Theoretical Yield (if needed)
If the initial amount of acetanilide used were given, we could calculate the theoretical yield. Since it’s not provided, we calculate actual yield only, based on the final mass obtained.
Explanation
In the synthesis of p-bromoaniline, a crucial intermediate is 4-bromoacetanilide, formed through the bromination of acetanilide. In Step 1 of the synthesis, bromine reacts with acetanilide in a 1:1 molar ratio to produce 4-bromoacetanilide via electrophilic aromatic substitution. This ratio implies that one mole of acetanilide yields one mole of 4-bromoacetanilide under ideal conditions.
From the data, the final mass of 4-bromoacetanilide obtained is 2.5 grams. Given its molecular weight is 214.06 g/mol, we use the formula: Moles=MassMolecular Weight\text{Moles} = \frac{\text{Mass}}{\text{Molecular Weight}}
Substituting the values gives approximately 0.01169 mol. This value represents the actual yield in moles. If we had the initial amount of acetanilide, we could compare this with the theoretical yield to determine the percent yield, which is essential for evaluating the efficiency of the reaction.
This yield can be affected by several experimental factors such as incomplete reaction, side products (e.g., ortho isomers), or losses during purification (e.g., recrystallization). Nevertheless, knowing the actual amount of product obtained is important for planning subsequent steps — like hydrolysis of the acetamide group to finally yield p-bromoaniline.
This analysis not only confirms product formation but also allows researchers to evaluate how well the reaction proceeded and how to optimize it. Accurately determining the yield is thus fundamental in synthetic organic chemistry.
