Other
Prepform synthesis lab 1b experiment 4.3 part 2
- Course
- Institution
Prepform synthesis lab 1b experiment 4.3 part 2
[Show more]
Seller
Follow
lisaverhoeven80
Reviews received
Content preview
Synthesis lab 1b (MOL126)Preparation form experiment 4.3b (LJV010)
Lisa Verhoeven, s1014716
27-2-2022
Synthesis of 1-bromo-1,2-
diphenylethene by
dehydrobromination of meso-
stilbene dibromide
Experimental aim
The aim of this experiment is to synthesise 1-bromo-1,2-diphenylethene by dehydrobromination of
meso-stilbene dibromide and to analyse it by means of TLC, melting point analysis, IR, H- and C-NMR
spectroscopy.
Background
Meso-stilbene dibromide can be de-hydrobrominated via an E2 reaction with a strong, non-
nucleophilic base such as hydroxide. As E2 reactions only proceed if the leaving group and
eliminating group can attain an anti-periplanar geometry, the de-hydrobromination of both
diastereomers of stilbene dibromide will yield (E)-1-bromo-1,2-diphenylethene. It could, however, be
that a small fraction of the meso-stilbene dibromide reacts via the E1 mechanism. As this E1
mechanism puts no constraint on the geometry of the transition state, also a very small fraction of
(Z)-1-bromo-1,2-diphenylethene might be formed. Hydroxide is very suitable for performing
elimination reactions because it is non-nucleophilic, as this minimises the extent to which the
competing SN2 reaction proceeds. The choice of solvent is very important to successfully synthesise
1-bromo-1,2-diphenylethene, as it is crucial to limit double dehydrobrominations and the resultant
synthesis of 1,2-diphenylethyne. As a much higher temperature is required for a second
dehydrobromination reaction to proceed because of its increased activation energy with respect to
the first dehydrobromination, solvents with a relatively low boiling point such as ethanol for example
(78◦C) are very suitable.
The dehydrobromination reaction can be monitored by means of TLC, as 1-bromo-1,2-
diphenylethene is less polar than meso-stilbene dibromide.
Figure 1. Reaction mechanism of the synthesis of 1-bromo-1,2-diphenyl ethene via the hydroxide-mediated dehydrobromination reaction
on meso-stilbene dibromide.
Experimental
1. Build the experimental set up
2. Put 0.8g meso-stilbene dibromide into the 3-necked flask
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller lisaverhoeven80. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $0.00. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
66781 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 15 years now