A number of common human foods and household ingestibles are toxic to dogs, including chocolate solids (theobromine poisoning), onion and garlic (thiosulphate, sulfoxide or disulfide poisoning), grapes and raisins, macadamia nuts, xylitol, as well as various plants and other potentially ingested materials. The nicotine in tobacco can also be dangerous. Dogs can get it by scavenging in garbage or ashtrays; eating cigars and cigarettes. Signs can be vomiting of large amounts (e.g., from eating cigar butts) or diarrhea. Some other signs are abdominal pain, loss of coordination, collapse, or death. Dogs are highly susceptible to theobromine poisoning, typically from ingestion of chocolate. Theobromine is toxic to dogs because, although the dog's metabolism is capable of breaking down the chemical, the process is so slow that even small amounts of chocolate can be fatal, especially dark chocolate.

Answer this question, if possible (if impossible, reply "unanswerable"): What is the chemical in chocolate that is poisonous to dogs?
theobromine