5Bromouracil

5-Bromouracil is a synthetic nucleobase analog of uracil in which a bromine atom occupies the 5-position of the pyrimidine ring. It is a halogenated pyrimidine and is used primarily in biochemical and genetic research. Its formula is C4H3BrN2O2 and its molecular weight is approximately 191 g/mol. In DNA, 5-bromouracil can be incorporated in place of thymine during replication when provided as a deoxyribonucleoside or deoxyribonucleotide; it is often used as a mutagen in laboratory experiments. While it typically pairs with adenine like thymine, 5-bromouracil can tautomerize to an enol form that mispairs with guanine, leading to base-substitution mutations during subsequent replications.

It is a parent compound for related nucleoside analogs; bromodeoxyuridine (BrdU), a deoxyribonucleoside analog used to label newly synthesized DNA, is derived from 5-bromouracil. Researchers use 5-bromouracil to study DNA replication fidelity, repair pathways, and mutagenesis in bacteria, yeast, and mammalian cells.

Chemically, 5-bromouracil is prepared by bromination of uracil under appropriate conditions. It is a hazardous mutagen and toxic; handling requires appropriate safety measures and disposal according to regulations.