Cyclobutyl bromide or bromocyclobutane is an organic compound containing a cyclobutane ring with one hydrogen atom replaced by bromine. The formula is C4H7Br.
Production Cyclobutyl bromide can be produced from cyclobutane carboxylic acid in a reaction with bromine in the presence of mercuric oxide. It can be made from silver cyclobutane carboxylate and bromine.
It can be made from cyclopropylmethanol, in a reaction with hydrogen bromide (HBr).
Cyclobutanol can react with HBr to yield cyclobutyl bromide.
Bromination of cyanocyclobutane produces a small amount of bromocyclobutane. In addition to the dominant product, 1-bromo-1-cyanocyclobutane.
Properties The lengths of the bonds in the bromocyclobutane molecule are as follows: Cα is carbon atom in position 1 adjacent to bromine. Cβ is the carbon in position 2 or 4 of the ring. Cγ is the carbon in position 3, opposite the bromine atom. Length Cα–Cβ = 1.540 Å. Length Cβ–Cγ = 1.548 Å. Length Cα–Br = 1.939 Å. The lengths of C–H = 1.096 Å, and C—D = 1.087 Å. The bond angles ∠ CβCγCβ = 88.1°, ∠ CβCαCβ = 88.7°, HCγH = 110.7°, HCβH = 108.7°, HCαBr = 111°. The angle of CβCαCβ plane with C–Br is 131.0°, and the dihedral angle (angle made by the normals of the CβCαCβ and CβCγCβ planes) is 29.35°.
There are two conformers based on the orientation of the bromine atom. The axial conformer comprises 3% of molecules, and the equatorial conformer comprises 97%. However there is a very low barrier to interconversion.
In the far-infrared spectrum there are Q-branch transitions at 143.0, 135.5, 129.2, and 124.0 cm-1.
The LF Raman spectrum has lines at 149.0, 139.5, 134.8, 128.5, 124.0 cm−1.
Refractive index N25D is 1.4768. Boiling point is 106-108°C. NMR spectrum +positioncis-transorientationshift Hzαaxial4.441βtransequatorial2.597βcisaxial2.465γcisequatorial2.094γtransaxial1.873
Reactions When heated to temperatures between at low pressure, hydrogen bromide is eliminated producing cyclobutene.
When heated around 436°C, butadiene and hydrogen bromide are produced.
Cyclobutyl bromide reacts with magnesium in ether solution to yield the Grignard reagent C4H7MgBr.
234 nm UV light photodissociates cyclobutyl bromide to form a cyclobutyl radical and atomic bromine.
Hydrogenation of bromocyclobutane yields cyclobutane. Cyclobutyl bromide can be reduced by Bu3SnH (or Bu3SnD) to cyclobutane.
Diphenylphosphide reacts in liquid ammonia to displace bromide to form cyclobutyldiphenylphosphine.
Tributylstannyllithium reacts with cyclobutyl bromide to form tributyl(cyclobutyl)tin.
Electro-oxidation of bromocyclobutane dissolved in acetonitrile yields N-cyclobutylacetamide.
Sodium methanesulfinate reacts with cyclobutyl bromide to yield some methylsulfonylcyclobutane.
In Lucas reagent (ZnCl2 + HCl), cyclobutyl bromide forms the cyclobutyl cation (c-C4H7+), which can rearrange or break the ring and then reform to yield cyclopropylcarbiny chloride (c-C3H5CH2Cl) and allylcarbinyl chloride (CH2=CHCH2CH2Cl).
Cyclobutyl bromide can do a carbon-carbon coupling to form 1,1'-bicyclobutyl c-C4H7-C4H7.
It is possible to substitute the bromine in bromocyclobutane with a trifluoromethyl, or trifluoroacetyl group under blue light.
References
Extra reading calculated specific heat, entropy, free energy and enthalpy