# Which is more stable: isobutylene or cis-2‐butene?

How do you compare which is more stable without using the heat of hydrogenation or combustion or any other numeric factual value: $$\ce{(CH3)2-C=CH2}$$ or $$\ce{CH3-CH=CH-CH3}$$ (cis)?

• Wouldn't we expect the most substituted alkene to be most (thermodynamically) stable? – electronpusher May 23 '19 at 16:25
• @electronpusher both the compounds have two methyl groups each. – Tapi May 23 '19 at 16:26
• @Karl I was taught "fill in the correct term for two substituents at the same carbon">trans>cis – Groverkss May 23 '19 at 17:59
• Numbers are better than intuition. Both alkenes have the same molecular formula. Heats of Formation (kcal/mol) are helpful: isobutylene (-4.3), (Z)-2-butene (-1.7). – user55119 May 23 '19 at 19:18
• @Groverkss You're right chemgapedia.de/vsengine/vlu/vsc/de/ch/12/oc/vlu_organik/alkene/… – Karl May 23 '19 at 20:12