1,8-Bis(dimethylamino)naphthalene Chemical Properties

Melting point:

49-51 °C(lit.)

Boiling point:

144-145°C (3.7505 mmHg)

Density 

1.12

Flash point:

>230 °F

storage temp. 

Keep in dark place,Inert atmosphere,Room temperature

solubility 

Soluble in organic solvents.

form 

Crystalline Powder

pka

12.1(at 25℃)

color 

Pale brownish-pink

Water Solubility 

insoluble

Sensitive 

Light Sensitive

Merck 

14,3388

BRN 

396782

InChIKey

GJFNRSDCSTVPCJ-UHFFFAOYSA-N

CAS DataBase Reference

20734-58-1(CAS DataBase Reference)

NIST Chemistry Reference

1,8-Naphthalenediamine, N,N,N',N'-tetramethyl-(20734-58-1)

Safety Information

Hazard Codes 

Xn,C

Risk Statements 

22-36/37/38-34

Safety Statements 

26-45-36/37/39

RIDADR 

3259

WGK Germany 

3

F 

8-10-23

HazardClass 

8

HS Code 

29215900

MSDS

• Language:English Provider:ACROS
• Language:English Provider:SigmaAldrich
• Language:English Provider:ALFA

1,8-Bis(dimethylamino)naphthalene Usage And Synthesis

Description

Significant attention in organic chemistry has been given to the so-called proton sponges, which are bi-center nitrogen bases that show spectacularly high basicity and very low nucleophilic character. The first member of this class of compounds 1,8-bis(dimethylamino)naphthalene or DMAN dragged attention due to its unexpectedly high basicity (pKa: DMAN 12.1; 1,8-diaminonaphthalene: 4.6) after its discovery in 1941[1]. It is prepared with an 82% yield from 1,8-diaminonaphthalene, dimethyl sulfate, and sodium hydride.

Chemical Properties

1,8-Bis(dimethylamino)naphtalene is pale brownish-pink crystalline powder

Uses

1,8-Bis(dimethylamino)naphthalene, also referred to as protone sponge, is a lipophilic proton trapping agent. 1,8-Bis(dimethylamino)naphthalene is used in the matrix for mass spectroscopy analysis of lipids and fatty acids.

Uses

Very strong base in organic synthesis and catalysis.

Uses

Very strong base with weak nucleophilic character due to steric effects.

Definition

ChEBI: N1,N1,N8,N8-tetramethylnaphthalene-1,8-diamine is a member of naphthalenes.

General Description

Proton-sponge is also referred as 1,8-dimethylamino naphthalene. It is very strong base with weak nucleophilic character due to steric effects. It also participates in the reactions between arachno-6,9-C₂B₈H₁₄ and selected acyl chlorides. It has been tested as an effective H⁺ scavenger.

Mechanism of action

A possibility of non-conventional two-step protonation of 1,8-bis(dimethylamino)naphthalene (proton sponge) is discussed. Unlike the generally accepted mechanism, involving relatively slow direct penetration of a proton into the cleft between the peri-NMe2 groups, it consists of the rapid addition of a proton to the out-inverted NMe2 group with the subsequent slower rotational transfer of the proton into the inter-nitrogen space to produce a stable chelated cation. The conclusion is that both pathways of proton sponge protonation, traditional and non-conventional, contribute in parallel with a still undefined ratio. The estimated out-basicity of the proton sponge is at least 5.5 orders of magnitude lower than the directly measured in-basicity[2].

Solubility in organics

Soluble in most organic solvents, such as methanol and chloroform.

Purification Methods

It is prepared by methylating 1,8-diaminonaphthalene, and likely impurities are methylated products. The tetramethyl compound is a stronger base than the unmethylated, di and trimethylated derivatives. The pKa values are: 1,8-(NH2)2 = 4.61, 1,8-(NHMe)2 = 5.61, 1-NHMe-8-NHMe2 = 6.43 and 1,8-(NMe2)2 = 12.34. The mixture is then treated with H2O at pH 8 (where all but the required base are protonated) and extracted with Et2O or CHCl3. The dried extract (K2CO3) yields the tetramethyldiamine on evaporation which can be distilled. It is a strong base with weak nucleophilic properties, e.g. it could not be alkylated by refluxing with EtI in MeCN for 4 days; and on treatment with methyl fluorosulfonate only the fluorosulfonate salt of the base is obtained. [NMR: Adler et al. J Chem Soc, Chem Commun 723 1968, Brown & Letang J Am Chem Soc 63 358 1941, Brzezinski et al. J Chem Soc Perkin Trans 2 857 1991.] Alternatively, crystallise proton sponge from EtOH and dry it in a vacuum oven. Store it in the dark in a CO2-free atmosphere. [Benoit et al. Can J Chem 65 996 1987, Beilstein 13 IV 344.]

References

[1] Utsab Bhattacharyya, Ralph Puchta, Renjith Thomas . “The proton sponge 1,8-bis(dimethylamino)naphthalene: The quicker-picker-upper also for s-block metal cations?” Chemical Physics Letters 777 (2021): Article 138735.
[2] Ozeryanskii, Valery A. et al. “Out-Basicity of 1,8-bis(dimethylamino)naphthalene: the experimental and theoretical challenge??.” Organic & Biomolecular Chemistry 15 (2013): 2360–2369.

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