I'm gonna parrot what most of the people here say, yes love is a chemical reaction in the brain, but so is every single thing we are able to perceive. That of course includes all emotions that we feel, every thought we have, and really even our ability to perform scientific experiments and observe the results. In fact everything we experience is a chemical reaction in the brain, because that's how the human brain works. So everything we see, hear, feel, taste, smell, or experience in anyway is the result of a chemical reaction in the brain, because that's how our brains process the universe around us. Our entire lives are just series complicated chemical reactions that we define as being "life", as is the life of anything we classify as "living".
Does that mean the emotions we feel like love aren't real? Fuck no! We're all chemical reactions all the time so emotion is just as real as anything else.
I will say that the line "love is a chemical reaction in the brain designed to compel animals to breed" is a load of steaming bullshit and piss fries though. Why? Because I'm asexual and I don't want to breed, nor am I able. I still form love based relationships with people, from non-sexual romantic relationships to bonds of friendship. So love exists as an emotion that is meant to strengthen cooperation and community amongst humans, which is a good thing.