Addition of HX to alkenes

7 real reactions from the literature, on styrenes, 1,1-disubstituted alkenes, α,β-unsaturated esters and trans-1,2-disubstituted alkenes. Each scheme shows starting materials, conditions and products, with the yield and reference where the source reports them.

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1. HX addition: methyl acrylate (an α,β-unsaturated ester) with HBr; CH3CH2OCH2CH3 gives methyl 3-bromopropanoate (the primary alkyl bromide).

   HX additionOrg. Synth. Coll. Vol. 3, p. 576

2. HX addition: indene (a styrene) with HCl gives 1-chloro-2,3-dihydro-1H-indene (the benzylic alkyl chloride).

   HX additionOrg. Synth. Coll. Vol. 2, p. 336

3. HX addition: a 1,1-disubstituted alkene with HCl gives the secondary alkyl chloride.

   HX additionJ. Org. Chem. 1987, 52, 462

4. HX addition: 7-methylidenedispiro[2.0.2~4~.1~3~]heptane (a 1,1-disubstituted alkene) with HBr gives 7-bromo-7-methyldispiro[2.0.24.13]heptane (the tertiary alkyl bromide).

   HX additionEur. J. Org. Chem. 2003, 4234

5. HX addition: trans-3-hexene (a trans-1,2-disubstituted alkene) with HCl gives 3-chlorohexane (the secondary alkyl chloride).

   HX additionJ. Am. Chem. Soc. 1939, 61, 940

6. HX addition: [(E)-prop-1-enyl]benzene (a styrene) with HBr gives (1-bromopropyl)benzene (the benzylic alkyl bromide).

   HX additionChem. Eur. J. 2017, 23, 12739

7. HX addition: cyclohexene (a six-membered cycloalkene) with KI, H3PO4; 80 °C gives iodocyclohexane (the secondary alkyl iodide).

   HX additionOrg. Synth. Coll. Vol. 4, p. 543