Butyl

The butyl group is an atomic group of the organic chemistry. It is one of the alkyl groups and derived formally from the structure of butane by abstraction of a hydrogen from. Thus it has the molecular formula C4H9. Butyl group, the four isomeric forms can occur: n-butyl, isobutyl, sec- butyl and tert- butyl group. While in the case of the n -butyl and iso -butyl group, the moiety is attached to a primary carbon atom, it is in the case of sec-butyl group attached to a secondary, in the case of the tert -butyl group on a tertiary.

Sec -butanol, sec-butyl group highlighted in blue.

Tert- butanol tert- butyl group highlighted in blue.

Sec - butyl radical, sec-butyl group highlighted in blue.

Tert- butyl radical, tert- butyl group highlighted in blue.

Properties

Steric properties

With increasing branching of the steric demand of the butyl groups increased. Tert- butyl groups provide sterically bulky radicals dar. they can be stabilized by chemical compounds, since an attack by the space-filling can be significantly hindered. The frustration also has an effect on the reaction kinetics, which thus can both accelerate and slow down. Running reaction that requires the engagement of a reactant in the vicinity of the tert- butyl group from, these reactions are mostly from significantly slower because of the attack by the bulky residue is prevented. The other way round is also the conformation of a molecule to be frozen by the tert- butyl radical in a position which is beneficial for the reaction kinetics, and thus accelerate the reaction. The tert -butyl group, in this case acts as an anchor.

Anchor groups

Iso -butyl and tert-butyl groups can be used as anchoring groups. This means that they impede their steric effect by changing the conformation of the compound. So they limit such as a free rotation of alkyl radicals or prevent the conversion of the two chair conformations of cyclohexane into each other. The bulky tert- butyl radical is preferably located in an equatorial position, as such give the slightest interactions with other substituents. In the second possible chair conformation, the rest is in an axial position, resulting in interactions with other axial substituents result ( Prelog voltage). Since these are energetically unfavorable, this equilibrium lies strongly on the side on which the tert- butyl group occupies an equatorial position.

Electronic Properties

Due to the different positions with which the butyl group binds to the molecule, resulting in different electronic properties, which are caused by the inductive effects of the alkyl groups. Among the isomeric butyl radicals, the electron density at the tertiary carbon of the tert-butyl group at the highest and the lowest n-butyl group. This is also reflected in the increasing basicity of the lithiated species of n -butyllithium over sec -butyllithium to give tert - butyl lithium. The same effect is also responsible for decreasing acidity of the alcoholic proton of the butyl alcohols, 1-butanol, 2-butanol and tert -butanol.

Use

Lithium alkyls are strong organometallic bases. They can be used to deprotonate weakly acidic protons and to lithiation. Butyllithiumbasen three commercially available as a standard reagent: n -butyllithium, sec-butyllithium and tert-butyllithium (rising reactivity). The tert-butyl group is an important component of the BOC protecting group.

The Hydrierungsagens diisobutylaluminum hydride ( DIBAL ) has two isobutyl.

Linkage groups

The following groups of substances contain all four isomeric forms of the butyl group as a structural element:

• Butanol
• Butylamines
• Butyl chlorides
• Butylbromide
• Butylbenzenes
• Leucine ( Butylglycine )
• Pentanals ( Butylcarbaldehyde )
• Pentanoic acids ( Butylcarbonsäuren )
• Acetate