Is there a way I can determine if a given hydrocarbon is an alkene, alkane or alkyne or even some other type. What are the KEY differences in them, like reactivity , ratio of elements and so on?

  • 2
    $\begingroup$ The NMR spectra a distinctly different $\endgroup$
    – Waylander
    Feb 5 at 11:07
  • $\begingroup$ What even is the NMR spectra $\endgroup$ Feb 5 at 12:13
  • 1
    $\begingroup$ If you really want to know start here: en.wikipedia.org/wiki/Nuclear_magnetic_resonance_spectroscopy $\endgroup$
    – Waylander
    Feb 5 at 13:03
  • $\begingroup$ Experimental determination can be done by using Baeyer's reagent or $\ce{Br₂ water}$. This, by far, is the qualitative analysis for it. $\endgroup$ Feb 5 at 13:26

1 Answer 1


Alkanes have nearly no reactions with any chemicals, at room temperature. They only react with $\ce{Cl2}$ and $\ce{Br2}$ to produce a haloderivate and some $\ce{HCl}$ or $\ce{HBr}$.

Alkenes react by oxidative addition to dilute alkaline permanganate, chlorine, bromine, iodine in alcohol, and ozone. They also react by simple addition with $\ce{HCl}$ (in the presence of $\ce{AlCl3}$) and other acids, like nitrous, sulfuric, hydrobromic, hydriodic. Alkenes also react by polymerization.

Alkynes react in a similarly way with the previous reagents, but they can have two successive addition reactions. Furthermore, if they possess the ynil group ($\ce{·CCH}$), they are also able to make copper or silver derivates with $\ce{Cu(NH3)2^+}$ and $\ce{Ag(NH3)2^+}$ solutions, in reactions like $$\ce{RCCH + Ag(NH3)2^+ -> RCCAg + NH4^+ + NH3}$$ $$\ce{RCCH + Cu(NH3)2^+ -> RCCCu + NH4^+ + NH3}$$ These two reactions are specific properties of the ynil group.


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