Carboxymethyl cellulose
Carboxymethyl cellulose (CMC) or cellulose gum is a cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand β linked D-glucose units....

Derivatization is a technique used in chemistry which transforms a chemical compound into a product of similar chemical structure, called a derivative....

 with carboxymethyl groups (-CH2-COOH) bound to some of the hydroxyl
A hydroxyl is a chemical group containing an oxygen atom covalently bonded with a hydrogen atom. In inorganic chemistry, the hydroxyl group is known as the hydroxide ion, and scientists and reference works generally use these different terms though they refer to the same chemical structure in...

 groups of the glucopyranose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...

A monomer is an atom or a small molecule that may bind chemically to other monomers to form a polymer; the term "monomeric protein" may also be used to describe one of the proteins making up a multiprotein complex...

s that make up the cellulose backbone
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...

. It is often used as its sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...

 salt, sodium carboxymethyl cellulose.


It is synthesized
Chemical synthesis
In chemistry, chemical synthesis is purposeful execution of chemical reactions to get a product, or several products. This happens by physical and chemical manipulations usually involving one or more reactions...

 by the alkali
In chemistry, an alkali is a basic, ionic salt of an alkali metal or alkaline earth metal element. Some authors also define an alkali as a base that dissolves in water. A solution of a soluble base has a pH greater than 7. The adjective alkaline is commonly used in English as a synonym for base,...

-catalyzed reaction
Chemical reaction
A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, such as heat, light or electricity...

 of cellulose with chloroacetic acid
Chloroacetic acid
Chloroacetic acid, industrially known as monochloroacetic acid is the organochlorine compound with the formula ClCH2CO2H. This carboxylic acid is a useful building-block in organic synthesis.-Production:...

. The polar (organic acid
An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...

) carboxyl groups render the cellulose soluble and chemically reactive.

The functional properties of CMC depend on the degree of substitution of the cellulose structure (i.e., how many of the hydroxyl groups have taken part in the substitution reaction), as well as the chain length of the cellulose backbone structure and the degree of clustering of the carboxymethyl substituents.


CMC is used in food science
Food science
Food science is a study concerned with all technical aspects of foods, beginning with harvesting or slaughtering, and ending with its cooking and consumption, an ideology commonly referred to as "from field to fork"...

 as a viscosity
Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...

 modifier or thickener, and to stabilize
Stabilizer (chemistry)
In chemistry a stabilizer is a chemical which tends to inhibit the reaction between two or more other chemicals. It can be thought of as the antonym to a catalyst...

An emulsion is a mixture of two or more liquids that are normally immiscible . Emulsions are part of a more general class of two-phase systems of matter called colloids. Although the terms colloid and emulsion are sometimes used interchangeably, emulsion is used when both the dispersed and the...

s in various products including ice cream
Ice cream
Ice cream is a frozen dessert usually made from dairy products, such as milk and cream, and often combined with fruits or other ingredients and flavours. Most varieties contain sugar, although some are made with other sweeteners...

. As a food additive, it has E number
E number
E numbers are number codes for food additives that have been assessed for use within the European Union . They are commonly found on food labels throughout the European Union. Safety assessment and approval are the responsibility of the European Food Safety Authority...

 E466. It is also a constituent of many non-food products, such as K-Y Jelly
K-Y Jelly
K-Y Jelly is a water-based, water-soluble personal lubricant produced by Johnson & Johnson. According to the company, "The origins of the brand name 'K-Y' are unknown...

, toothpaste
Toothpaste is a paste or gel dentifrice used with a toothbrush as an accessory to clean and maintain the aesthetics and health of teeth. Toothpaste is used to promote oral hygiene: it serves as an abrasive that aids in removing the dental plaque and food from the teeth, assists in suppressing...

, laxative
Laxatives are foods, compounds, or drugs taken to induce bowel movements or to loosen the stool, most often taken to treat constipation. Certain stimulant, lubricant, and saline laxatives are used to evacuate the colon for rectal and/or bowel examinations, and may be supplemented by enemas under...

s, diet
Diet (nutrition)
In nutrition, diet is the sum of food consumed by a person or other organism. Dietary habits are the habitual decisions an individual or culture makes when choosing what foods to eat. With the word diet, it is often implied the use of specific intake of nutrition for health or weight-management...

 pills, water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

-based paint
Paint is any liquid, liquefiable, or mastic composition which after application to a substrate in a thin layer is converted to an opaque solid film. One may also consider the digital mimicry thereof...

s, detergent
A detergent is a surfactant or a mixture of surfactants with "cleaning properties in dilute solutions." In common usage, "detergent" refers to alkylbenzenesulfonates, a family of compounds that are similar to soap but are less affected by hard water...

s, textile sizing
Sizing or size is any one of numerous specific substances that is applied to or incorporated in other material, especially papers and textiles, to act as a protecting filler or glaze....

 and various paper
Paper is a thin material mainly used for writing upon, printing upon, drawing or for packaging. It is produced by pressing together moist fibers, typically cellulose pulp derived from wood, rags or grasses, and drying them into flexible sheets....

 products. It is used primarily because it has high viscosity
Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...

, is non-toxic, and is hypoallergenic
Hypoallergenic, meaning "below normal" or "slightly" allergenic, was a term first used in a cosmetics campaign in 1953. It is used to describe items that cause or are claimed to cause fewer allergic reactions...

. In laundry detergents it is used as a soil suspension polymer designed to deposit onto cotton and other cellulosic fabrics creating a negatively charged barrier to soils in the wash solution. CMC is used as a lubricant
A lubricant is a substance introduced to reduce friction between moving surfaces. It may also have the function of transporting foreign particles and of distributing heat...

 in non-volatile
Volatility (chemistry)
In chemistry and physics, volatility is the tendency of a substance to vaporize. Volatility is directly related to a substance's vapor pressure. At a given temperature, a substance with higher vapor pressure vaporizes more readily than a substance with a lower vapor pressure.The term is primarily...

 eye drop
Eye drop
Eye drops are saline-containing drops used as a route to administer medication in the eye. Depending on the condition being treated, they may contain steroids, antihistamines, sympathomimetics, beta receptor blockers, parasympathomimetics, parasympatholytics, prostaglandins, non-steroidal...

s (artificial tears). Sometimes it is methyl cellulose (MC) which is used, but its non-polar methyl groups (-CH3) do not add any solubility or chemical reactivity to the base cellulose.

Following the initial reaction the resultant mixture produces approximately 60% CMC plus 40% salts (sodium chloride
Sodium chloride
Sodium chloride, also known as salt, common salt, table salt or halite, is an inorganic compound with the formula NaCl. Sodium chloride is the salt most responsible for the salinity of the ocean and of the extracellular fluid of many multicellular organisms...

 and sodium glycolate). This product is the so-called Technical CMC which is used in detergents. A further purification process is used to remove these salts to produce pure CMC which is used for food, pharmaceutical and dentifrice (toothpaste) applications. An intermediate "semi-purified" grade is also produced, typically used in paper applications.

CMC is also used in pharmaceuticals as a thickening agent.
CMC is also used in the oil drilling industry as an ingredient of drilling mud, where it acts as a viscosity modifier and water retention agent. Poly-anionic cellulose or PAC is derived from CMC and is also used in oilfield practice.

Insoluble microgranular carboxymethyl cellulose is used as a cation-exchange resin in ion-exchange chromatography for purification of proteins. Presumably the level of derivatization is much lower so that the solubility properties of microgranular cellulose are retained while adding sufficient negative charged carboxylate groups to bind positively charged proteins.

CMC is also used in ice packs
Ice pack
An ice pack or gel pack is a plastic sac of ice, refrigerant gel or liquid, or, in an emergency, even frozen vegetables. The refrigerant, usually non-toxic, can absorb a considerable amount of heat, since its enthalpy of fusion is high...

 to form a eutectic mixture
Eutectic system
A eutectic system is a mixture of chemical compounds or elements that has a single chemical composition that solidifies at a lower temperature than any other composition. This composition is known as the eutectic composition and the temperature is known as the eutectic temperature...

 resulting in a lower freezing point and therefore more cooling capacity than ice.

Aqueous solutions CMC have also been used to disperse carbon nanotubes. It is thought that the long CMC molecules wrap around the nanotubes, allowing them to be dispersed in water.

External links

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