Tert-Butyl alcohol

• Tert- butyl
• Trimethylcarbinol

Colorless solid with kampherartigem odor

Fixed

0.79 g · cm -3 ( 20 ° C)

26 ° C.

83 ° C.

41.2 hPa ( 20 ° C)

Completely miscible with water

Risk

2740 mg · kg -1 ( LD50, rat, oral)

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Tert- butanol (including tert-butyl alcohol or 2-methyl -2-propanol ) is the simplest tertiary alcohol.

Production and representation

Is recovered 2-methyl -2-propanol by electrophilic addition of water to isobutylene in the presence of sulfuric acid as the catalyst:

In this reaction, is almost exclusively the 2- methyl -2-propanol, and not the isomeric 2-methyl- 1-propanol ( isobutanol), as it is formed during the initial protonation of the isobutene by the sulfuric acid only stable tert- butyl cation ( Markovnikov rule).

Properties

Physical Properties

2-methyl -2-propanol is a slightly above room temperature, melting, solid, colorless substance that smells characteristic camphor. The compound is a tertiary alcohol: The carbon atom bearing the hydroxy group is bonded to three other carbon atoms. As all the butanols, 2- methyl -2-propanol -flammable.

Thermodynamic properties

The vapor pressure function is given by Antoine corresponding log10 (P) = A- ( B / ( T C )) ( P in bar, T in K) with A = 4.49774, B = 1174.869 and C = -93, 92 in the temperature range from 312.66 to 355.56 K. the temperature dependence of the enthalpy of vaporization can be determined according to equation ΔVH0 = A · e ( - αTr ) (1- Tr) β ( ΔVH0 in kJ / mol, Tr = (T / Tc ) reduced temperature ) with A = 69.085 kJ / mol, α = -0.3583, β = 0.678 and Tc = 506.2 K describe the temperature range between 298 K and 385 K.

Temperature dependence of the heat of vaporization of tert-butanol

Safety characteristics

2-methyl -2-propanol is a flammable solid. The compound has a flash point of 11 ° C, which means it can form an inflammable vapor - air mixture below the melting point on the solid 2-methyl- 2-propanol. The explosion range is between 1.7 vol% (52 g/m3) as the lower explosive limit ( LEL) and 8 % by volume (250 g/m3 ) and upper explosive limit (UEL ). The ignition temperature is 470 ° C. The fabric falls within the temperature class T1.

Chemical Properties

Such as all aliphatic alcohols, the hydroxyl group of the 2 -methyl-2 -propanol can be deprotonated and the obtained tert- butylate anion. A well known and often used in organic synthesis chemistry salt is the potassium tert- butoxide, which is accessible with elemental potassium, for example, by reaction of 2 -methyl-2 -propanol.

This highly basic salt is used as bulky and therefore only weakly nucleophilic base application, for example in Deprotonation Reactions in which the base or attack nucleophilic. Often used then 2-methyl -2-propanol as the solvent.

Strong protic acids (hydrochloric acid, sulfuric acid, phosphoric acid, etc. ), 2- methyl -2-propanol is protonated at the oxygen atom, and with the elimination of water, the tert- butyl cation which is stabilized by the three methyl groups Hyperkonjugationseffekt forms. In the presence of good nucleophiles, the reaction proceeds in terms of a nucleophilic substitution (SN1 ) on. For example, the 2- chloro-2- methylpropane (tert -butyl chloride ) forms very easily from 2- methyl -2-propanol and concentrated hydrochloric acid. Are not suitable nucleophiles present (for example, with the use of sulfuric acid or phosphoric acid), the reaction proceeds in the sense of elimination of (E1) to give 2- methyl propene ( isobutylene ). This is the reverse of the preparation of 2 -methyl-2 -propanol.

Use

Tert- butanol is used as a fuel additive ( anti-knock agent ). Further, the alcohol used as the starting material for the synthesis of tert- butyl esters and t-butylphenols which are in turn used as antioxidants. It also uses it in the gas chromatographic determination of blood alcohol concentration ( headspace - GC) as internal standard. Furthermore, tert- butanol is used as an additional denaturant for drinking alcohol ( ethanol).

In synthetic chemistry, it is, inter alia, also be used for the disposal of residues of the alkali metals potassium, sodium and, as it reacts therewith controllably tert- Butanolaten.

Safety

2-methyl -2-propanol may irritate the skin and eye contact. When inhaled, it causes coughing continues, thus it is also absorbed by the body. If swallowed, may cause nausea and vomiting. Following absorption, drowsiness, dizziness, respiratory paralysis, hypotension and cardiovascular disorders may occur. 2-methyl -2-propanol is slightly hazardous to water ( Water hazard class 1).