|Preferred IUPAC name
3D model (JSmol)
|Molar mass||129.25 g·mol−1|
|Density||0.742 g mL−1|
|Melting point||−50 to −46 °C (−58 to −51 °F; 223 to 227 K)|
|Boiling point||126.6 °C; 259.8 °F; 399.7 K|
|4.01 g/L (at 20 °C)|
|Vapor pressure||4.1 kPa (at 37.70 °C)|
Refractive index (nD)
|GHS signal word||DANGER|
|H225, H301, H314, H412|
|P210, P273, P280, P301+310, P305+351+338, P310|
|Flash point||10 °C (50 °F; 283 K)|
|Lethal dose or concentration (LD, LC):|
LD50 (median dose)
|200–500 mg kg−1 (oral, rat)|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
N,N-Diisopropylethylamine, or Hünig's base, is an organic compound and an amine. It is named after the German chemist Siegfried Hünig. It is used in organic chemistry as a base. It is commonly abbreviated as DIPEA, DIEA, or i-Pr2NEt.
DIPEA consists of a central nitrogen that is bonded to an ethyl group and two isopropyl groups. A lone pair of electrons resides on the nitrogen atom, which can react with electrophiles. However, as the two isopropyl groups and the ethyl group occupy much of the space surrounding the nitrogen, only small electrophiles such as protons can react with the nitrogen lone pair.
Occurrence and preparation
Pure DIPEA exists as a colorless liquid, although commercial samples can be slightly yellow. If necessary, the compound can be purified by distillation from potassium hydroxide or calcium hydride.
Uses and reactions
DIPEA is a hindered base that is commonly employed as an acid or proton scavenger. Thus, like 2,2,6,6-tetramethylpiperidine and triethylamine, DIPEA is a good base but a poor nucleophile, a combination of properties that makes it a useful organic reagent.
It is commonly used as the hindered base in amide coupling reactions between a carboxylic acid (typically activated, for example, as an acid chloride, as illustrated below) and a nucleophilic amine. As DIPEA is hindered and poorly nucleophilic, it does not compete with the nucleophilic amine in the coupling reaction.
DIPEA has been investigated for its use as a selective reagent in the alkylation of secondary amines to tertiary amines by alkyl halides. This is often hampered by an unwanted Menshutkin reaction forming a quaternary ammonium salt but this side-reaction is absent when DIPEA is present.
Transition metal catalyzed cross-coupling reactions
Examples of DIPEA used as a substrate
Comparison with triethylamine
DIPEA and triethylamine are structurally very similar, with both compounds considered hindered organic bases. Due to their structural similarity, DIPEA and triethylamine can be used interchangeably in most applications. The nitrogen atom in DIPEA is more shielded than the nitrogen atom in triethylamine. However, triethylamine is a slightly stronger base than DIPEA; the pKas of the respective conjugate acids in dimethyl sulfoxide are 9.0 and 8.5, respectively.
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