Glycoazodyes (or GADs) are a family of "naturalised" synthetic dyes, so called because they are the conjugation of common commercial

azo dyes Azo dyes are organic compounds bearing the functional group R−N=N−R′, in which R and R′ are usually aryl and substituted aryl groups. They are a commercially important family of azo compounds, i.e. compounds containing the C−N=N−C li ...

with

sugar Sugar is the generic name for sweet-tasting, soluble carbohydrates, many of which are used in food. Simple sugars, also called monosaccharides, include glucose Glucose is a sugar with the Chemical formula#Molecular formula, molecul ...

through a "linker". This principle is summarised in the scheme below.

Generations, Structure, and Synthesis

First-generation

The first-generation of Glycoazodyes was first reported in 2007. These Glycoazodyes use a

diester In chemistry, an ester is a compound derived from an acid (either organic or inorganic) in which the hydrogen atom (H) of at least one acidic hydroxyl group () of that acid is replaced by an organyl group (R). These compounds contain a distinc ...

linker, specifically a

succinyl Succinic acid () is a dicarboxylic acid with the chemical formula (CH2)2(CO2H)2. In living organisms, succinic acid takes the form of an anion, succinate, which has multiple biological roles as a metabolic intermediate being converted into fum ...

bridge. An

ester In chemistry, an ester is a compound derived from an acid (either organic or inorganic) in which the hydrogen atom (H) of at least one acidic hydroxyl group () of that acid is replaced by an organyl group (R). These compounds contain a distin ...

group bonds the sugar to an n-

alkane In organic chemistry, an alkane, or paraffin (a historical trivial name that also has other meanings), is an acyclic saturated hydrocarbon. In other words, an alkane consists of hydrogen and carbon atoms arranged in a tree structure in whi ...

spacer, and the spacer bonds to the dye through another

group.

Synthesis

First-generation Glycoazodyes are synthesized using

glucose Glucose is a sugar with the Chemical formula#Molecular formula, molecular formula , which is often abbreviated as Glc. It is overall the most abundant monosaccharide, a subcategory of carbohydrates. It is mainly made by plants and most algae d ...

galactose Galactose (, ''wikt:galacto-, galacto-'' + ''wikt:-ose#Suffix 2, -ose'', ), sometimes abbreviated Gal, is a monosaccharide sugar that is about as sweetness, sweet as glucose, and about 65% as sweet as sucrose. It is an aldohexose and a C-4 epime ...

lactose Lactose is a disaccharide composed of galactose and glucose and has the molecular formula C12H22O11. Lactose makes up around 2–8% of milk (by mass). The name comes from (Genitive case, gen. ), the Latin word for milk, plus the suffix ''-o ...

as the sugar group. The point of

ification is controlled by selectively protecting alcohol groups on the sugar, or by choosing an azo dye with a different alcohol group position. The dye or the sugar group can be succinylated by reacting a free alcohol group with

succinic anhydride Succinic anhydride, is an organic compound with the molecular formula (CH2CO)2O. This colorless solid is the acid anhydride of succinic acid. Preparation In the laboratory, this material can be prepared by dehydration of succinic acid. Such dehy ...

. The resulting hemisuccinate then reacts with a free alcohol group on the dye or the sugar. The condensation product is then deprotected.

Second-generation

The second-generation of Glycoazodyes was first reported in 2008. These Glycoazodyes use an etherel linker. An ether group bonds the sugar and the dye to an n-

spacer, and the spacer bonds to the dye through another ether group. Like first-generation Glycoazodyes, second-generation Glycoazodyes use glucose, galactose or lactose as the sugar group.

Synthesis

Like first-generation Glycoazodyes, second-generation Glycoazodyes are synthesized using a

, or

sugar group. The point of the

ether In organic chemistry, ethers are a class of compounds that contain an ether group, a single oxygen atom bonded to two separate carbon atoms, each part of an organyl group (e.g., alkyl or aryl). They have the general formula , where R and R� ...

bond is controlled by selectively protecting alcohol groups on the sugar, or by choosing an

azo dye Azo dyes are organic compounds bearing the functional group R−N=N−R′, in which R and R′ are usually aryl and substituted aryl groups. They are a commercially important family of azo compounds, i.e. compounds containing the C−N=N−C l ...

with a different alcohol group position. An unprotected alcohol group of either the sugar or the dye is reacted with an n-carbon, terminal dibromoalkane in a solution of

potassium hydroxide Potassium hydroxide is an inorganic compound with the formula K OH, and is commonly called caustic potash. Along with sodium hydroxide (NaOH), KOH is a prototypical strong base. It has many industrial and niche applications, most of which utili ...

and 18-crown-6 ether, using non-

anhydrous A substance is anhydrous if it contains no water. Many processes in chemistry can be impeded by the presence of water; therefore, it is important that water-free reagents and techniques are used. In practice, however, it is very difficult to achie ...

tetrahydrofuran Tetrahydrofuran (THF), or oxolane, is an organic compound with the formula (CH2)4O. The compound is classified as heterocyclic compound, specifically a cyclic ether. It is a colorless, water- miscible organic liquid with low viscosity. It is ...

as the

solvent A solvent (from the Latin language, Latin ''wikt:solvo#Latin, solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a Solution (chemistry), solution. A solvent is usually a liquid but can also be a solid, a gas ...

. The potassium hydroxide produces an

alkoxide ion In chemistry, an alkoxide is the conjugate base of an alcohol and therefore consists of an organic group bonded to a negatively charged oxygen atom. They are written as , where R is the organyl substituent. Alkoxides are strong bases and, when ...

from the alcohol while the 18-crown-6 ether acts as a phase-transfer agent. The reaction proceeds through a classic SN-2

nucleophilic substitution In chemistry, a nucleophilic substitution (SN) is a class of chemical reactions in which an electron-rich chemical species (known as a nucleophile) replaces a functional group within another electron-deficient molecule (known as the electrophile) ...

. A terminal Bromo group is eliminated, and a bond is formed between the oxygen of the alcohol and the carbon of the alkane. An ether is produced between the n-carbon linker and the sugar or the dye. At this stage, the terminal Bromo group that remains may react under the same conditions with the free alcohol of a corresponding sugar or dye. The condensation product is then deprotected.

Third-generation

The third-generation of Glycoazodyes was first reported in 2015. These Glycoazodyes use an amido-ester linker. An

amide In organic chemistry, an amide, also known as an organic amide or a carboxamide, is a chemical compound, compound with the general formula , where R, R', and R″ represent any group, typically organyl functional group, groups or hydrogen at ...

group bonds the sugar to an n-

spacer, and the spacer is bonded to the dye through an

group.

Synthesis

Third-generation Glycoazodyes are synthesized using

amino sugar In organic chemistry, an amino sugar is a sugar molecule in which a hydroxyl group has been replaced with an amine group. More than 60 amino sugars are known, with one of the most abundant being N-Acetylglucosamine, ''N''-acetyl--glucosamine (a 2- ...

s such as 6-amino-6-deoxy-D-galactose or 6' amino-6'-deoxylactose. The point of the amide bond is controlled by protecting the alcohol groups on the sugar and allowing the free amine to react. The point of the ester group is controlled by choosing a azo dye with a different alcohol group position. Either the dye or the sugar is reacted with

. This forms an

group with the sugar or an

group with the dye. The free

carboxylic acid In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an Substituent, R-group. The general formula of a carboxylic acid is often written as or , sometimes as with R referring to an organyl ...

may then react with the alcohol group or amine group on the corresponding dye or sugar. The condensation product is then deprotected.

Properties

A variety of fabrics such as

wool Wool is the textile fiber obtained from sheep and other mammals, especially goats, rabbits, and camelids. The term may also refer to inorganic materials, such as mineral wool and glass wool, that have some properties similar to animal w ...

silk Silk is a natural fiber, natural protein fiber, some forms of which can be weaving, woven into textiles. The protein fiber of silk is composed mainly of fibroin and is most commonly produced by certain insect larvae to form cocoon (silk), c ...

nylon Nylon is a family of synthetic polymers characterised by amide linkages, typically connecting aliphatic or Polyamide#Classification, semi-aromatic groups. Nylons are generally brownish in color and can possess a soft texture, with some varieti ...

polyester Polyester is a category of polymers that contain one or two ester linkages in every repeat unit of their main chain. As a specific material, it most commonly refers to a type called polyethylene terephthalate (PET). Polyesters include some natura ...

, polyacrylic, polyacetate, and

polyurethane Polyurethane (; often abbreviated PUR and PU) is a class of polymers composed of organic chemistry, organic units joined by carbamate (urethane) links. In contrast to other common polymers such as polyethylene and polystyrene, polyurethane term ...

may be dyed with Glycoazodyes under moderate temperatures and pressures in aqueous solutions. First-generation Glycoazodyes dye

cotton Cotton (), first recorded in ancient India, is a soft, fluffy staple fiber that grows in a boll, or protective case, around the seeds of the cotton plants of the genus '' Gossypium'' in the mallow family Malvaceae. The fiber is almost pure ...

poorly. However, second-generation Glycoazodyes dye

effectively.

Wool Wool is the textile fiber obtained from sheep and other mammals, especially goats, rabbits, and camelids. The term may also refer to inorganic materials, such as mineral wool and glass wool, that have some properties similar to animal w ...

dyed with Glycoazodyes shows good fastness when exposed to the

ISO The International Organization for Standardization (ISO ; ; ) is an independent, non-governmental, international standard development organization composed of representatives from the national standards organizations of member countries. Me ...

105-C06 washing and

105 X12 rubbing tests. Glycoazodyes vary in their water solubility. They may be soluble in cold to warm water and may dissolve after stirring or upon addition. Minor variations in

absorption spectra Absorption may refer to: Chemistry and biology * Absorption (biology), digestion ** Absorption (small intestine) * Absorption (chemistry), diffusion of particles of gas or liquid into liquid or solid materials * Absorption (skin), a route by whic ...

occur when Glycoazodye solutions are prepared, using water, acetone, or methanol solvents. Converting a parent

to a Glycoazodye may produce a small hypsochromic shift in the absorption spectra.

Environmental impact

Several properties may make Glycoazodyes an environmentally friendly alternative to traditional

synthetic dyes A Colourant, colorant is any substance that changes the spectral transmittance or reflectance of a material. Synthetic colorants are those created in a laboratory or industrial setting. The production and improvement of colorants was a driver of th ...

. The increased hydrophilicity of Glycoazodyes allows for the elimination of

surfactant Surfactants are chemical compounds that decrease the surface tension or interfacial tension between two liquids, a liquid and a gas, or a liquid and a solid. The word ''surfactant'' is a Blend word, blend of "surface-active agent", coined in ...

mordant A mordant or dye fixative is a substance used to set (i.e., bind) dyes on fabrics. It does this by forming a coordination complex with the dye, which then attaches to the fabric (or tissue). It may be used for dyeing fabrics or for intensifying ...

s, and

salts In chemistry, a salt or ionic compound is a chemical compound consisting of an assembly of positively charged ions ( cations) and negatively charged ions (anions), which results in a compound with no net electric charge (electrically neutral). ...

, during the dyeing process and permits the aqueous dying of a variety of

textile Textile is an Hyponymy and hypernymy, umbrella term that includes various Fiber, fiber-based materials, including fibers, yarns, Staple (textiles)#Filament fiber, filaments, Thread (yarn), threads, and different types of #Fabric, fabric. ...

s at moderate temperatures and pressures. The unique structure may also allow for the treatment of textile effluent through biological means. ''

Fusarium oxysporum ''Fusarium oxysporum'' (Schlecht as emended by Snyder and Hansen), an ascomycete fungus, comprises all the species, varieties and forms recognized by Wollenweber and Reinking within an infrageneric grouping called section Elegans. It is part of ...

'' efficiently decolourizes the first-generation Glycoazodye 4-azobenzene. Various other

Ascomycota Ascomycota is a phylum of the kingdom Fungi that, together with the Basidiomycota, forms the subkingdom Dikarya. Its members are commonly known as the sac fungi or ascomycetes. It is the largest phylum of Fungi, with over 64,000 species. The def ...

fungi show a similar potential to decolourise Glycoazodyes, but to a lesser extent. Detoxification has been measured, using the ''

Daphnia magna ''Daphnia magna'' is a small planktonic crustacean (adult length 1.5–5.0 mm) that belongs to the subclass Phyllopoda. Description ''Daphnia magna'' is a typical water flea of the genus ''Daphnia''. The females reach up to 5 mm in ...

'' acute toxicity test, showing a 92% dye detoxification after 6 days. This detoxification method produces low concentrations of

nitrobenzene Nitrobenzene is an aromatic nitro compound and the simplest of the nitrobenzenes, with the chemical formula C6H5 NO2. It is a water-insoluble pale yellow oil with an almond-like odor. It freezes to give greenish-yellow crystals. It is produced ...

aniline Aniline (From , meaning ' indigo shrub', and ''-ine'' indicating a derived substance) is an organic compound with the formula . Consisting of a phenyl group () attached to an amino group (), aniline is the simplest aromatic amine. It is an in ...

, and

nitrosobenzene Nitrosobenzene is the organic compound with the chemical formula, formula C6H5NO. It is one of the prototypical organic nitroso compounds. Characteristic of its functional group, it is a dark green species that exists in equilibrium with its pale ...

External links

* http://onlinelibrary.wiley.com/doi/10.1002/ejoc.200600686/abstract

References

{{Note, Bartalucci Azo dyes Organic pigments Carbohydrate chemistry Carbohydrates