(1 pts) Literature melting point of (E,E)-1,4-diphenyl-1,3-butadiene From the procedure 10. Measure the melting point of both your crude product and your recrystallized product. Record these values on the data sheet. 139.0- 148.7°C Melting point of crude product: Melting point of recrystallized product: 145.1 – 148.4 °C (0.5pts) Melting point of crude product (°C) 139.0-148.7 Saved (0.5pts) Melting point of recrystallized product (°C) 145.1-148.4 Does the melting point obtained for your product indicate that your sample is (E,E)-1,4-diphenyl-1,3-butadiene? Or a mixture of isomers? Normal . BIU X2 X – === f TX (2pts) Was there a difference in the melting point of the crude and the melting point of the recrystallized product?
The Correct Answer and Explanation is:
Correct Answer:
Yes, there was a difference in the melting point between the crude and recrystallized product. The crude product had a melting point range of 139.0–148.7 °C, while the recrystallized product had a narrower range of 145.1–148.4 °C.
Explanation:
The melting point data indicates that there was a significant difference between the crude and recrystallized samples of (E,E)-1,4-diphenyl-1,3-butadiene, both in terms of temperature range and purity. The crude product exhibited a broad melting point range (139.0–148.7 °C), which is characteristic of an impure substance. Impurities disrupt the regular lattice structure of a compound, causing it to melt over a wider temperature range and at a lower temperature than the pure compound.
In contrast, the recrystallized product had a narrower and slightly higher melting range (145.1–148.4 °C), indicating improved purity. This narrower range is much closer to the literature melting point of pure (E,E)-1,4-diphenyl-1,3-butadiene, which typically falls around 147–150 °C. The narrowing of the melting point range and the shift toward the expected literature value after recrystallization confirms that many of the impurities present in the crude sample were effectively removed through recrystallization.
While the recrystallized product does not perfectly match the upper end of the literature range, it is very close and within expected experimental error. Therefore, it is reasonable to conclude that the purified product is predominantly (E,E)-1,4-diphenyl-1,3-butadiene. The small deviations could be due to minor residual impurities or experimental limitations in temperature measurement.
The difference in melting point behavior between the crude and recrystallized samples is a strong indicator of successful purification. Overall, the melting point analysis supports that the recrystallized product is much purer and more likely to be the desired (E,E)-isomer, rather than a mixture of isomers or an impure sample.
Correct Answer:
Yes, there was a difference in the melting point between the crude and recrystallized product. The crude product had a melting point range of 139.0–148.7 °C, while the recrystallized product had a narrower range of 145.1–148.4 °C.
Explanation:
The melting point data indicates that there was a significant difference between the crude and recrystallized samples of (E,E)-1,4-diphenyl-1,3-butadiene, both in terms of temperature range and purity. The crude product exhibited a broad melting point range (139.0–148.7 °C), which is characteristic of an impure substance. Impurities disrupt the regular lattice structure of a compound, causing it to melt over a wider temperature range and at a lower temperature than the pure compound.
In contrast, the recrystallized product had a narrower and slightly higher melting range (145.1–148.4 °C), indicating improved purity. This narrower range is much closer to the literature melting point of pure (E,E)-1,4-diphenyl-1,3-butadiene, which typically falls around 147–150 °C. The narrowing of the melting point range and the shift toward the expected literature value after recrystallization confirms that many of the impurities present in the crude sample were effectively removed through recrystallization.
While the recrystallized product does not perfectly match the upper end of the literature range, it is very close and within expected experimental error. Therefore, it is reasonable to conclude that the purified product is predominantly (E,E)-1,4-diphenyl-1,3-butadiene. The small deviations could be due to minor residual impurities or experimental limitations in temperature measurement.
The difference in melting point behavior between the crude and recrystallized samples is a strong indicator of successful purification. Overall, the melting point analysis supports that the recrystallized product is much purer and more likely to be the desired (E,E)-isomer, rather than a mixture of isomers or an impure sample.
