Issue with diene halogenation-1 (VCL 3-1)

When performing the diene halogenation-1 reaction (VCL 3-1) as indicated (1,3-butadiene, ether, HCl, ice bath, with or without condenser), the reaction proceeds to form 3-chloro-1-butene and eventually go to completion, but no spots appear on the TLC plate either during the reaction or after it’s complete.

Also,when working up the reaction with water, the organic product is not extracted into ether but remains in the water layer, and it must be isolated by distillation. Has anyone experienced this? I’m not certain if it’s really an issue or I’m doing something wrong. Thanks!

Hi JAC,

Great questions! The butadiene reactant and the chlorinated product are both highly volatile. They do not remain on the TLC plate long enough to be tracked, that is why the software has no spots on the plate for this reaction.

You are correct about the extraction, and we are adjusting this worksheet and others to correct mistakes in the directions about which layer to keep. You are also correct that you need to do a distillation to separate the water from the 3-chloro-1-butadiene. You may already know how to do this, but if not here is a link to a video on how to do it in Beyond Labz - https://www.youtube.com/watch?v=t73aSkYgH5s&list=PLr9DtLFbhGPFCdW_MV8iJMyBcHfRIMlvs&index=2

  • Kelsey

Thanks for the clarification on the TLC analysis. Regarding the extraction, I think that even low molecular weight chlorinated hydrocarbons (e.g., 3-chloro-1-butene in VCL 3-1 and 1-chloro-2-butene in VCL 3-3) should be more soluble in ether than in water, and would end up in the ether layer during extraction.

The data bank used for the solubility indicated that these compounds are not soluble in ether.

  • Kelsey