Comments on: Making Alkyl Halides From Alcohols

By: Madhav Mittal

Madhav Mittal — Wed, 29 May 2024 10:41:26 +0000

According to the Quick N Dirty guide for Sub. and eli. , in case of 2 degree alcohol when we will treat it with HCL, we get a good leaving group(H2O) and a strong nucleophile(Cl-),so the major pathway should be SN2 but not SN1.How in this case we have to assume SN1?

By: James Ashenhurst

James Ashenhurst — Thu, 02 Feb 2023 03:33:19 +0000

In reply to karla. H2O will react with hydrogen halides to give H3O+ X-. The product will likely be the alcohol, not the halide.

By: karla

karla — Wed, 01 Feb 2023 15:52:09 +0000

Sir, may I ask why dry hydrogen halides are used as opposed to aqueous solutions of HX?

By: James Ashenhurst

James Ashenhurst — Fri, 12 Aug 2022 03:02:53 +0000

In reply to Arpan Goswami. You can think of the hydride as acting a bit like a nucleophile in an SN2 reaction where the hydride shift happens about the same time as breakage of the C-O bond. That's probably the best way to look at it.

By: Arpan Goswami

Arpan Goswami — Sun, 17 Apr 2022 18:19:20 +0000

Sir I have a small confusion. When we use lucas reagent ie ZnCl2 the oxygen of the alcohol coordinates to the zinc center which converts it into a good leaving group. But does using ZnCl2 + HCl in case of primary alcohols promotes Sn1? Cause I have seen a bunch of problems where they have asked to write the product when a primary alcohol is treated with lucas reagent but in all of them they have shown 1,2 shifts which can’t take place unless Sn1 is followed. But apparently as you said and I found in many other sources Sn2 should obviously be taking place.

By: Arpan Goswami

Arpan Goswami — Fri, 07 May 2021 02:48:29 +0000

I am confused how reaction of lucas reagent with primary alcohol with one branching at the beta carbon proceeds (say ch3ch2ch(ch3)ch2oh ). Does it follow Sn1 or Sn2

By: James Ashenhurst

James Ashenhurst — Thu, 06 Feb 2020 21:29:46 +0000

In reply to Andrew R.. It wouldn't be dimethyl zinc, since the methyl group in dimethyl zinc is similar in basicity to that of a Grignard reagent (and will be destroyed by water just as easily). Zinc does form strong bonds with oxygen, however...

By: Andrew R.

Andrew R. — Fri, 31 Jan 2020 20:19:24 +0000

Hi. In the Lucas reagent synthesis of methyl chloride fr. MeOH + HCl + ZnCl2… Does the excess water in HCl lead to the formation of dimethyl zinc chloride or something else, at all? The answer is two complex for my pea brain, haha

By: James Ashenhurst

James Ashenhurst — Fri, 18 Oct 2019 19:09:27 +0000

In reply to Alan.

In a substitution reaction, a bond breaks and forms on the same carbon. The reactant which contains that carbon is called the “substrate”.

In nucleophilic substitution, the substrate reacts with a nucleophile (e.g. an alcohol) and a new C-O bond forms and a C-X (carbon-halide) bond breaks.

There is also a reaction called electrophilic substitution. In electrophilic substitution, the substrate (e.g. benzene) reacts with an electrophile (e.g. Br+) resulting in formation of a C-Br bond and breaking of a C-H bond. Still substitution, but since the substrate is reacting with an electrophile, it’s called “electrophilic substitution”.

There is also such a thing as free radical substitution.

By: Alan

Alan — Thu, 17 Oct 2019 08:34:05 +0000

Why is this resaction considered an nucleophilic substitution and not an electrophilic substitution?