2-Bromobutane CAS 78-76-2 is a secondary butyl bromide used as a sec-butylating reagent, a Grignard precursor, and an intermediate for pharmaceuticals, agrochemicals, and some fragrance work. Buyers often compare it with 1-bromobutane because both have the formula C4H9Br, but they are not drop-in substitutes. Shanghai Arise New Material Co., Ltd. supplies 2-bromobutane as a colorless transparent liquid (MW 137.02, typical purity ≥99%) for process teams that specifically need the secondary isomer.
The first difference is structure and reactivity. 2-Bromobutane is a secondary alkyl halide (bromine on carbon-2). It undergoes substitution and elimination differently from primary 1-bromobutane. SN2 is slower; E2 and rearrangement risks are higher. If your route needs a linear n-butyl group, you want 1-bromobutane. If you need a sec-butyl group on carbon, nitrogen, or oxygen, you specify 2-bromobutane CAS 78-76-2.
The second difference is organometallic behavior. 2-Bromobutane reacts with magnesium to form a sec-butyl Grignard reagent. Initiation, Wurtz coupling, and residual water limits are still critical, but the resulting nucleophile is branched. Do not assume a procedure written for n-butyl bromide will give the same yield or impurity map.
The third difference is downstream use. 2-Bromobutane is used as a solvent and organic-synthesis intermediate, as a raw material for sedative, anesthetic, and other drug intermediates, and in selected fragrance synthesis. It is an intermediate, not a finished API or perfume oil.
Physical data also diverge. 2-Bromobutane (EINECS 201-140-7) melts around −112°C, boils around 91°C, and has a density of about 1.255 g/mL. It is a highly flammable liquid and vapor with a flash point near 21°C. Many GHS files classify it as Danger, with severe skin burns and eye damage. Inhalation of high vapor may cause headache, dizziness, nausea, or vomiting. Store it tightly closed in a dry, well-ventilated place, often at 2–8°C, away from heat, sparks, flames, oxidizers, and strong bases. Use appropriate gloves, flame-retardant antistatic clothing, and good ventilation. Absorb spills; do not wash to drains.
Purchasing should always name the isomer. Write "2-bromobutane CAS 78-76-2," not "bromobutane." Incoming GC should show the 2-isomer, not a mixed C4 bromide stream. Packing is typically 1 L bottles, 25 L, 200 L, or 1000 L IBC.
If your process needs a sec-butyl handle rather than n-butyl, contact Shanghai Arise New Material Co., Ltd. for a sample and COA of 2-bromobutane CAS 78-76-2. Share whether the next step is Grignard, pharmaceutical intermediate, or agrochemical alkylation so we can match assay, water limit, and packing.
