# Lucas test in the presence of EWG like -CN

Does the given compound give Lucas test?

My teacher says due to the presence of a strong electron withdrawing group the carbocation formed is unstable.

But I say if it undergoes $$\mathrm{S_N2}$$ mechanism then an electron withdrawing group should increase its reactivity. Why then does this compound not give the test?

• Do you think Lucas reagent (ZnCl2, dil. HCl) will favor SN2 reaction pathway? – Rahul Verma Sep 5 '20 at 3:06
• @RahulVerma Yes I do. Is it correct. Or do they undergo only SN1 reaction – ishwar b b Sep 5 '20 at 4:28
• Thats a cyanohydrin not a standard alcohol – Waylander Sep 5 '20 at 7:13
• @ishwarbb Side note, for future reference: It is very welcome to illustrate the structure of organic molecules with a sketcher. You may both improve the representation further, as well demonstrate you understand the structure of organic molecules, if the three atoms $\ce{N#C-C}$ are depicted aligned in a straight line. Sketchers often offer to «clean the structure» for you with a click on a dedicated button. – Buttonwood Sep 7 '20 at 12:13
• @Buttonwood ok I will keep that in mind – ishwar b b Sep 7 '20 at 12:37

Lucas reagent follows SN1 pathway. $$\ce{Zn}$$ is a lewis acid that tends to bond with $$\ce{-OH}$$ and form a partial positive charge leading to the formation of a carbocation.
Similarly, the primary and secondary alcohols, need to form a primary and secondary carbocation, which is not stable. Hence the reaction is slow. Zinc forms a weaker bond with $$\ce{-OH}$$ and induces a partial charge on them, thus not forming the whole carbocation.