Isosorbide

• D- isosorbide
• 1,4:3,6 - dianhydro -D-sorbitol
• 1,4:3,6 - dianhydro -D-glucitol
• (3R, 3aR, 6S, 6aR ) hexahydro- furo [3,2 -b] furan-3 ,6-diol

White, odorless, crystalline, hygroscopic solid

Fixed

1.30 g · cm -3

61-64 ° C

Decomposes above 270 ° C

• Soluble in water (> 850 g · l -1) alcohols, dioxane, ketones
• Practically insoluble in hydrocarbons, esters, ethers,

25.8 g · kg -1 ( LD50, rat, oral)

Template: Infobox chemical / molecular formula search available

Isosorbide is a bicyclic chemical compound from the group of diols, and the oxygen-containing heterocycles, wherein the two furan rings are fused. Starting material for isosorbide, D - sorbitol, which is obtained by catalytic hydrogenation of D- glucose, which in turn is produced by hydrolysis of starch. Isosorbide is therefore discussed as a plant-based platform chemical that can be derived from the biodegradable derivatives of different functionality.

As a monomer unit for biopolymer polycarbonates, polyesters, polyurethanes and epoxies isosorbide currently takes great scientific and technical interest.

Production and representation

Isosorbide obtained by acid-catalyzed bimolecular dehydration of D- sorbitol, wherein the initially formed monocyclic furanoid sorbitan, from which by further dehydration gives the bicyclic Furofuran derivative isosorbide is formed.

The reaction yields about 70 to 80% isosorbide next 30-20 % undesired by-products which can be relatively expensive, by distillation, recrystallization from alcohols, recrystallization from the melt, or by a combination of these methods or by deposition from the vapor phase. The high purity ( > 99.8 %) of the isosorbide as a monomer is essential for achieving high molecular weights and undyed products.

Properties

Isosorbide is a white crystalline solid which is highly hygroscopic in moist air. The different orientation of the secondary hydroxyl groups in the V-shaped arranged bicyclic system leads to different physical properties and chemical reactivity, and therefore permits selective Monoderivatisierung of isosorbide. The hydroxy group in position 5 is endo constantly and together with the oxygen atom in the adjacent furan ring, a hydrogen bridge. This causes the hydroxy group in 5-position and nucleophilic reactive than the exo - position hydroxy group in position 2; However, it is shielded stronger against the attack of bulky reactants.

Use

Isosorbide

Because of its strong hygroscopicity, isosorbide is used as a humectant, in medicine as an osmotic diuretic to treat hydrocephalus and acute narrow-angle glaucoma. The two secondary hydroxy groups make isosorbide to a versatile platform chemical from renewable resources. The diol isosorbide etc. can be derivatized mono- or bifunctional and converted into compounds with interesting property profiles as well as monomer for novel polymers with standard reactions of organic chemistry, such as nitration, esterification, etherification, tosylation.

Isosorbidnitrate

The by nitration of isosorbide with conc. Nitric accessible 2.5 - isosorbide dinitrate (ISDN) is suitable as its major metabolite 5 - mononitrate ( ISMN ) because of its vasodilator effect for the treatment of angina pectoris.

Isosorbidester

In the esterification of isosorbide with fatty acids Isosorbidmonoester are available which are suitable because of their surface-active properties as detergents in household cleaners, dishwashing detergents and cosmetic preparations. Which is also easily accessible Isossorbiddiester be used as dispersants for pigments, preservatives, polymer stabilizers, emulsifiers for cosmetics, and as plasticizers for vinyl polymers, especially polyvinyl chloride (PVC).

Isosorbidether

Isosorbidether, in particular the simplest representative, 2,5- dimethyl isosorbide (DMI ) find increasingly used as a sustainable solvent for cosmetic and pharmaceutical preparations and as an electrolyte additive for lithium - ion batteries and as a fuel additive for diesel.

Isosorbidphosphate

Phosphoric acid derivatives of isosorbide be explored as an environmentally friendly alternative to halogenated flame retardants. As a replacement for the extruded for imparting flame retardancy of polystyrene foams (XPS ) in the construction industry for building insulation as SVHC ( "substance of very high concern " ) since May 2013, a ban on production and use of 1,2,5,6,9,10 - hexabromocyclododecane occupied (HBCD ) are inter alia phosphorus- based Isosorbidverbindungen such as Isosorbide bis ( diphenyl phosphate, ISTP ) into consideration.

ISTP is easily accessible by transesterification of isosorbide with triphenyl phosphate in the presence of potassium carbonate at 150 ° C. The strength as a yellowish oil in 88 % yield obtained isosorbide -bis- diphenyl phosphate contains about 20% by weight dimer. The high decomposition temperature of ISTP allows use in XPS, the strong plasticizing effect, however, is disturbing. Particularly pronounced is the flame retardancy in the presence of sulfur-containing synergist, such as Bis ( diphenylphosphinothionyl ) disulfide ( BDP ), so that at 3 wt % ISTP the minimum requirement of fire protection class B2 is satisfied.

Polymers of isosorbide

The now good availability and the high thermal stability of the isosorbide make this diol from renewable raw materials interesting as a monomer for thermoplastic (bio ) polymers such as polyesters and polycarbonates, and for thermosetting resins such as polyurethanes or epoxy resins. The hydroxyl groups can be transferred via the tosylates and azides into primary amino groups, or by addition of acrylonitrile followed by hydrogenation in high yield into the corresponding Aminopropylderivate that as starting materials for diisocyanates - of diamines at the most - for the representation of polyurethanes suitable polyamides or as a curing agent for epoxy resins.

The replacement of monoethylene glycol (MEG ) as the diol in the polyester is polyethylene terephthalate (PET ) leads to Polyisosorbidterephthalat (PIT ), which by an extremely high thermal stability (up to 360 ° C under nitrogen) is characterized. However, due to the lower reactivity of the secondary hydroxyl groups in isosorbide relatively low molecular weights and high residual amounts of terephthalic acid which lead to the low chemical stability of the resulting polymers. Therefore, today with isosorbide polyesters and MEG are examined as diol components which exhibit improved properties, such as less discoloration.

Of particular interest is isosorbide as a monomer in polycarbonate where it could replace the identified as xenoestrogens bisphenol A. The problem with isosorbide -based polycarbonates is their unsatisfactory temperature resistance and impact resistance, which is improved by the addition of comonomers to isosorbide or polymer blends.

In polyurethanes isosorbide itself can function as a diol or as a building block for the polyol used as the diisocyanate and chain extender. By reacting isosorbide with epichlorohydrin obtained isosorbide- bisglycidyl ether ( bis - epoxide), that as a substitute for the analogous bisphenol A -bis- epoxide with suitable curing agents, such as Polyamines or cyclic acid anhydrides to thermosetting epoxy resins can be implemented that are used as adhesives, paints or coatings of cans for food.

Next polyoxazolidones are described by reaction of isosorbide diglycidyl ethers with diisocyanates that may find use in the electrical and electronics industry as a rigid, highly branched and solvent-resistant thermosets.

Isosorbide is a versatile platform chemical from renewable resources, which are now also available in industrial quantities of tens of thousands of tons / year in Europe ( Roquette Frères SA ) and the USA ( Cargill, Inc. and Archer Daniels Midland Co.) is available. For particularly promising at present is the use of isosorbide as a comonomer in PET bottles as a raw material and as a substitute for bisphenol A, kept particularly in thermoset polycarbonates.

Safety

With an LD50 value of 24.15 g · kg -1 ( rat, oral) isosorbide similar non-toxic, such as D -glucose, also with an LD50 of 25.8 g · kg -1 ( rat, oral) and is of the Food and Drug Administration FDA classified as GRAS ( " generally recognized as safe") substance.