JPS6021982B2 - New imidazole compound, method for synthesizing the compound, and method for preventing rust of silver metal using the compound - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel imidazole compound, and particularly to a compound that exhibits a mackerel-proofing effect on coated metals.

It has been known that certain imidazole compounds exhibit a rust-preventing effect on copper metal.

(For example, Special Publications No. 46-17046 and No. 48-114)
However, although known imidazole compounds such as 2-undecyl imidazole or 2-undecyl-4-methylimidazole are effective in preventing rust on copper metal, they do not rust prevent at all on coated metal. Shows no effect.

The present inventors have discovered that imidazole has anti-rust effect on silver.
As a result of intensive research in search of 2-ethyl-4[51-methylimidazolyl[5{4]
1] - Discovered that disulfide corresponds to this.

It is noteworthy that the above compounds exhibit excellent rust-preventing effects on silver metals, but not only do they not exhibit fin-preventing effects on copper metals, but they also have the property of causing copper to turn black. are doing. The difference in this behavior is not well understood. In any case, it is a fact that the above-mentioned compounds have an anti-competitive effect on silver, and this is an interesting phenomenon. When synthesizing the compound of the present invention, 1 mole of 2-ethyl-4-methylimidazole and 1 to 3 g atoms of elemental sulfur (preferably 2 g Atom) and 1 to 5 moles (preferably 3 moles) of dimethyl sulfoxide (hereinafter referred to as DMSO) are subjected to a temporary reaction under heating, and the reaction between the three produces water and methyl sulfide. Water and methyl sulfide are DMS
Together with a portion of O, a mixture with a low boiling point (28 to 35%) is created, and the mixture is taken out of the system from the cooler.

During the course of the reaction, this mixture is constantly removed from the system, so that under appropriate heating, the temperature within the system does not become very high due to the latent heat of vaporization. If external heating is performed more than necessary, DMS○ (the boiling point of DMSO is much higher than a mixture with a low boiling point) will come out, which is not preferable. Therefore, heating during synthesis requires boiling point 2
It is desirable to heat the crab to such an extent that 8 to 35 qo of crab matter continues to come out.If such heating is performed, the internal temperature will drop to about 100 qo.
The end point of the reaction is maintained at a temperature of 28-3500 m
) may be used as the point at which crabs stop appearing.

The usual reaction time in the present invention is about 1 calm hour. After the reaction is completed, the reaction mixture is subjected to steam distillation to remove DMSO from the system, and hot Hakama acid is added to the residue until it becomes acidic, then allowed to cool, and then filtered through a furnace to collect the furnace liquid. . An appropriate amount of activated carbon is added to the furnace liquid and the mixture is filtered again to collect the furnace liquid. The thus obtained furnace liquid was dried under reduced pressure using a rotary evaporator. The dried product is dissolved in water, Na2CQ is added thereto until no foaming occurs, the precipitated crystals are collected in a furnace, and after being purified once with hot water, they are dried to obtain the desired product.
2-ethyl-4-methylimidazole, elemental sulfur and D
The three-way synthesis method for MSO was described above, but of course DMSO
It is also possible to further add other solvents to the above three.

However, when benzene, methanol, water, etc. were added in particular, the yield decreased significantly, so there seems to be no advantage in further adding solvents other than DMSO. The physical properties of the novel compound 2-ethyl-4{5'-monomethylimidazolyl-[5'4-]-disulfide in the present invention are as follows.

Melting point: Approximately 130°C Solubility: Insoluble in water, acetone, CC14, CHC13.

Easy to MeOH, AcOH, HClap. Basicity: Sea bream”, : 1585, 1518, 1422 (first absorption)
, 1380 (second absorption), 1312, 1279, 119
5, 1107, 1066, 1037, Satoshi 2, 960, 8
70, 78F 742, 660NMR (CF3COOH
): 61.44, bait, t(zoCH2CH3); 62.3
4 8th, s (end C day 3); 63.1 Riyama, q (Na C day 2-C9 group) NESS: m/e 282 (M+), 174
, 142, 141, 127, 109 8G 73, 59
, 56, 42... TLC:
R "0.80 ~ 0.95 (Alumina, H of E): R〆0
．． 72 to 0.57 (siliency, EtOH), all 12 colors.

Next, regarding the coin protection method for plated metal in the present invention, the compound is dissolved in a suitable organic solvent to form a solution,
The solution is brought into contact (coating,
It is sufficient to simply remove the solvent adhering to the surface.

The surface of silver metal treated in this way maintains its brightness even after being left in the air for a long time, and no specular blackening is observed.

In carrying out the present invention, it is possible to make a paste by mixing a suitable abrasive and the above-mentioned solvent, and it is also possible to obtain a rust prevention effect by polishing the silver surface with the paste. Since this means contact between the solution and silver, it goes without saying that it is within the scope of the present invention. The present invention will be explained in detail below using examples.

Example 1 A condenser was attached to the reaction vessel below (from horizontal).
-Ethyl-4-methylimidazole 55 mol (0.5 mol), DMSOI 17 mol (1.5 mol) and elemental sulfur 32
Acetate (1.0 gram atom) was charged and heated under the presence of flies.

The reaction starts soon after heating starts, and the boiling point is low (28-35
The crab portion of qo) has started to come out. Since crab release stopped after 10 hours of heating, steam was introduced into the system and DMSO was distilled off by steam distillation.

Hakama acid (20 minutes) was added to the residue while it was hot until the system became acidic. After cooling, it was filtered and the furnace liquid was collected. Activated carbon was added to the furnace liquid for 5 days, and the mixture was further filtered to collect the furnace liquid. N was added to this furnace until CQ stopped foaming, and the precipitated crystals were taken out of the furnace, washed once with hot K, and then dried to obtain the target disulfide (67% yield vs. imidazole). I got it.
The TLC of this product is R〆0.59-0.67 (silica,
EtOH, 12 colors). Example 2 2-Ethyl-4'51-methylimidazolyl-[5'4']-disulfide was dissolved in methanol.1. After making a skin t% solution and polishing the surface by soaking gauze in the solution, I lightly wiped the right half of a pure silver plate (1.5 melon x 10) that had been washed alternately with methanol and acetone. I left it indoors.

Claims (1)

[Claims] 1. 2-ethyl-4(5)-methylimidazolyl-[5(4)]-disulfide represented by the structural formula ▲ Numerical formulas, chemical formulas, tables, etc. are available▼. 2 Synthesis of 2-ethyl-4(5)-methylimidazolyl-[5(4)]-disulfide characterized by heating reaction of 2-ethyl-4-methylimidazole and elemental sulfur in a dimethylsulfoxide solvent Law. 3 2-ethyl-4(5
)-Methylimidazolyl-[5(4)]-disulfide synthesis method. 4 2-ethyl-4(5)-methylimidazolyl-[5
(4)] - A method for preventing rust of silver metal, which comprises dissolving disulfide in an organic solvent, bringing the solution into contact with the surface of silver metal, and volatilizing the organic solvent adhering to the surface of silver metal.