1936 was when molotovs were made. Fire had been around for thousands of years. Alcohol had been around for thousands of years. Most people knew that alcohol could be lit on fire. Why did it take so long for a Molotov cocktail to be invented? Especially since whenever a new technology is made the first thing that happens is that it’s attempted to be weaponized.
It seems your premise is mistaken: a Molotov Cocktail cannot be made from alcohol. The term refers to fuels like gasoline/petrol in a glass bottle. During the Winter War (1939), Finns fighting the Soviet Union dubbed these improvised weapons as a sarcastic tribute to Soviet foreign minister Vyacheslav Molotov.
While such weapons may have existed on some level a few decades before this, they couldn’t be that much older, since they require a situation where such highly combustible liquid fuels are quite common.