Suberate

Oxalic (Hibdrate) Malonio Sttooinio Qluiaric Adipic Pimclic Suberic Aiclaic Scbacic Malic Mocic Fumaric Maleic Meaaoonic Citraconic Itaoonio Camphoric roC Tartaric mcco Tartaric d.Tartahc. Citric (hydrated) Aconitic... 

Glutarlc acid (n =3), pimelic acid (n = 5) and suberic acid (n = 6) may be obtained from the corresponding dibromides. These are converted by aqueous - alcoholic potas-sium or sodium cyanide into the dinitriles, and this latter are smoothly hydrolysed by 50 per cent, sulphuric acid into the dicarboxybc acids ... 

Suberic acid. Prepare hexamethylene dibromide from hexamethy-lene glycol (Section 111,15) according to the procedure described in Section 111,35). Convert the 1 6-dibromohexane, b.p. H4r-115°/12 mm., into hexamethylene dicyanide, b.p. 178-180°/15 mm., by refluxing it with a 20-25 per eent. excess of aqueous - alcoholic sodium cyanide solution (compare Section 111,114), distilling off the hquid under diminished... 

Heat a mixture of hexamethylene dicyaiiide with 15 times its weight of 50 per cent, sulphuric acid by weight under reflux for 10 hours. The acid crystallises out on cooling. Filter oflF the suberic acid upon a sintered glass funnel, and recrystallise it from acetone m.p. 141-142°. The yield is 90 per cent, of the theoretical. 

Pimelic acid. This may be prepared from 1 5-peiitanediol or tetra-hydropyran, through the dibromide (Sections 111,35 and 111,37) and dinitrile exactly as described for Suberic Acid. An alternative method for the preparation of 1 5-dibromopentane, together with full details of the subsequent steps, is given in the following Section. 

To some extent each of these objections is met by the presence of either chemical or crystallite crosslinking in the polymer. Another approach which complements the former is to incorporate rings into the backbone of the chemical chain. As an example, contrast the polyesters formed between ethylene glycol and either suberic or terephthaUc acid. Structures [V] and [VI], respectively, indicate the repeat units in these polymers ... 

Subeconomic resources Suberic acid Suberic acid [505-48-6] Subject matter Sublimation dyes... 

Other by-products formed are relatively easy to separate, including esters of higher unsaturated monobasic acids (alkyl 3-pentenoate and 3,5-heptadienoate) (5) and esters of multiply-unsaturated dibasic acids, eg, suberates. 

The compound is not effective when appHed as a preharvest dormancy agent on potatoes and it should not be used until injuries to the tuber coat have healed. Neither should it be appHed until some suberization has occurred, generally two weeks after storage at >10° C (23). CIPC is widely used outside the United States on a number of crops as a herbicide. 

Order of thermal stabiUty as determined by differential thermal analysis is sebacic (330°C) > a2elaic = pimelic (320°C) > suberic = adipic = glutaric (290°C) > succinic (255°C) > oxahc (200°C) > malonic (185°C) (19). This order is somewhat different than that in Table 2, and is the result of differences in test conditions. The energy of activation for decarboxylation has been estimated to be 251 kj/mol (60 kcal/mol) for higher members of the series and 126 kJ/mol (30 kcal/mol) for malonic acid (1). 

Suberic Acid. This acid is not produced commercially at this time. However, small quantities of high purity (98%) can be obtained from chemical supply houses. If a demand developed for suberic acid, the most economical method for its preparation would probably be based on one analogous to that developed for adipic and dodecanedioic acids air oxidation of cyclooctane to a mixture of cyclooctanone and cyclooctanol. This mixture is then further oxidized with nitric acid to give suberic acid (37). 

Another method that appears to have commercial potential is the ozonolysis of cyclooctene. Ozonolysis is carried out using a short chain carboxyHc acid, preferably propanoic acid, as solvent. The resultant mixture is thermally decomposed in the presence of oxygen at about 100°C to give suberic acid in about 60—78% yield (38—40). Carboxylation of 1,6-hexanediol using nickel carbonyl as catalyst is reported to give suberic acid in 90% yield (41). 

There are several laboratory methods useful for the preparation of suberic acid. One starting material is 1,6-hexanediol which can be converted to the dibromide with HBr. Reaction of the dibromide with NaCN gives the dinitrile which can be hydrolyzed to suberic acid. The overall yield is 76% (42). Another laboratory method is the condensation of 1,3-cyclohexanedione with ethyl bromoacetate foUowed by reductive cleavage to give suberic acid in 50% yield (43). 

Suberic acid (hexane-l,6-dicarboxylic acid) [505-48-6] M 174.2, m 141-142°, pK pKj 5.40. Crystd from acetone and sublimes at 300° without dec. 

Detection and result The chromatogram was freed from mobile phase and immersed for 3 s in the dipping solution and heated to 125°C for 5 — 10 min. The carboxylic acids terephthalic acid (tiRi 5), succinic acid (fiRi 50 — 55), phthalic acid (hRf 55 — 60), suberic acid (tiRi 60 — 65), sebacic acid (fiRi 65 — 70), benzoic acid (tiRi 75 — 80) and salicylic acid (hRf 80 — 85) yielded brown zones on a light brown background. The detection limit was 2 pg acid per chromatogram zone. 

Even before heating all the acids rapidly appeared as blue zones on a yellow-blue background. After heating tartaric acid QiRf 2—5) and maUc acid hRf 5 — 10) retained their color while lactic acid hRf 30 — 35), succinic acid hRf 35—40), pimelic acid hRf 50), maleic acid hRf 55), suberic acid hRf 55 — 60), benzoic acid hRf 80 — 85), stearic acid hRf 85 — 90) and arachidic acid hRf 85—90) appeared as pale yellow zones on a blue-yellow background (Fig. 1). The detection limits lay at 1 to 2 pg substance per chromatogram zone. 

Fig. 1 Schematic representation of the chromatographic separation of carboxylic acids. Maleic acid (1), pimelic acid (2), succinic acid (3), benzoic acid (4), malic acid (5), tartaric acid (6), lactic acid (7), stearic acid (8), arachidic acid (9), suberic acid (10), mixture (M).

Detection and result The chromatogram was dried in a stream of warm air for 10 min, immersed in the reagent solution for 3 s and then subjected to intense UV radiation (high pressure lamp, A = 365 nm) for up to 10 min. Terephthalic (hRf 0 - 5), pimelic (hRf 55), suberic (hRf 60), sebacic (hRf 65 — 70) and benzoic acids (hRf 70 — 75) together with sorbic, malic, adipic, citric, tartaric, lactic and fumaric acids only exhibited a reaction on silica gel layers at higher concentrations. 4-Hydroxybenzoic, salicylic and acetylsalicylic acids fluoresced light blue after irradiation. The detection limit per chromatogram zone was 0.5 pg for salicylic acid and more than 5 pg for benzoic acid. 

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