The boiling point of ethyl ethanoate (ethyl acetate) was measured at 71 degrees Celsius, significantly lower than the true boiling point of 77.1 degrees Celsius. This discrepancy is attributed to the presence of impurities, particularly more volatile substances such as water or unreacted ethanol, which can form a positive azeotrope with ethyl acetate. The discussion highlights that impurities with lower volatility typically raise the boiling point, while those with higher volatility can lower it. The recommendation is to dry the liquid using a molecular sieve and re-measure the boiling point to confirm the presence of azeotropes.
PREREQUISITESChemists, chemical engineers, and laboratory technicians involved in organic synthesis and distillation processes, particularly those working with ethyl acetate and its derivatives.
Daniel2244 said:
Yeah, that makes more sense. However, is the reason my boiling point is lower than the true value because of an azeotrope?Borek said:
Not necessarily. However, if it is not, the boiling point should not be constant, but rise in the course of the distillation as the more volatile substance will boil off first.Daniel2244 said:
Could you explain differently because I do not understandDrDu said:
So essentially could I say: the ethyl acetate I made has a lower BP then the true value which shows it contains impurities. The ethyl acetate contains an azeotrope for example water or un-reacted ethanol which is more volatile than ethyl acetate which causes the Bp to decrease . I'm not sure if this is correct or not, the research I am doing only tells me why the bp increase whereas I'm look for why my bp is lower then the true value.Borek said:
Daniel2244 said:
So why is my boiling point lower than the true. I know you're probably annoyed with me keep asking but I do not understand why my BP is lower.HAYAO said:
Daniel2244 said:
I'm not annoyed
, and most likely neither are everyone else.Well, due to my temperature being lower than true value I believe it is a positive azeotrope because the boiling point is lower than the constituents. If I am right the new interaction between ethyl acetate and water are weaker and can escape into vapour easier. But it still doesn't explain how impurity affects the bp.HAYAO said:You are overthinking. DrDu and Borek are simply stating the general idea for you to understand the underlying concepts, so that it will help you draw out conclusions based on those concepts.
The general idea is that low-volatile impurity will raise the boiling point of the mixture, as Borek said.
Another general idea is that there are positive and negative azeotropes, which means the boiling point of the mixture at the azeotrope composition is lower or higher than any of the component alone, as implicitly stated by DrDu.
What do you think is the contributing factor for your case, based on your obtained experimental results?
I'm not annoyed
Daniel2244 said:
Ok, so could I say impurities such as unreacted chemicals would have caused my decrease in temperature due to different volatility of ethonal and ethanoic acids. Additionally, they could be an positive azeotrope in the ethyl acetate I produced which also causes the Bp to decrease due to weaker interactions between molecules therefore vapor can escape more easily.Borek said:
At this point, I don't know how you define "impurity". Since you are talking about distillation of ethyl acetate, even ethanol and water in this distilled ethyl acetate are impurities.Daniel2244 said:
Like Borek said, yes.
Very good point. The mixture have two layers. However, having two layers does not mean that each layer is completely pure in composition. The upper layer is ethyl acetate rich, and the lower layer is water rich. As an azeotrope, upper and lower layer contain 97 wt% and 9 wt% of ethyl acetate, respectively (Azeotrope Tables by Wikipedia).
If the impurity(ies) has lower volatility than ethyl acetate then the bp rises, generally speaking. However, positive azeotrope causes bp to lower. In this particular case, the latter is the main contribution over the former.Daniel2244 said:
HAYAO said:
DrDu said: