What is Nitriles?
A nitrile is any organic compound that has a -C≡N functional group. The prefix cyano- is used interchangeably with the term nitrile in industrial literature. Nitriles are found in many useful compounds, including methyl cyanoacrylate, used in super glue, and nitrile butadiene rubber, a nitrile-containing polymer used in latex-free laboratory and medical gloves. Organic compounds containing multiple nitrile groups are known as cyanocarbons.
Inorganic compounds containing the -C≡N group are not called nitriles, but cyanides instead. Though both nitriles and cyanides can be derived from cyanide salts, most nitriles are not nearly as toxic.
How to make Nitriles?
MAKING NITRILES
This page looks at various ways of making nitriles - from halogenoalkanes (haloalkanes or alkyl halides), from amides, and from aldehydes and ketones. It pulls together information from pages dealing with each of these kinds of compounds
Making nitriles from halogenoalkanes
The halogenoalkane is heated under reflux with a solution of sodium or potassium cyanide in ethanol. The halogen is replaced by a -CN group and a nitrile is produced. Heating under reflux means heating with a condenser placed vertically in the flask to prevent loss of volatile substances from the mixture.
The solvent is important. If water is present you tend to get substitution by -OH instead of -CN.
Note: A solution of potassium cyanide in water is quite alkaline, and contains significant amounts of hydroxide ions. These react with the halogenoalkane. This reaction is discussed on the page about the reactions between halogenoalkanes and hydroxide ions.
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For example, using 1-bromopropane as a typical halogenoalkane:
You could write the full equation rather than the ionic one, but it slightly obscures what's going on:
The bromine (or other halogen) in the halogenoalkane is simply replaced by a -CN group - hence a substitution reaction. In this example, butanenitrile is formed.
Note: If you want the mechanisms for these reactions (which differ depending on exactly what sort of halogenoalkane you are talking about), you can find them by following this link.
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Making a nitrile by this method is a useful way of increasing the length of a carbon chain. Having made the nitrile, the -CN group can easily be modified to make other things - as you will find if you explore the nitriles menu (link a the bottom of the page).
Making nitriles from amides
Nitriles can be made by dehydrating amides.
Amides are dehydrated by heating a solid mixture of the amide and phosphorus(V) oxide, P4O10.
Water is removed from the amide group to leave a nitrile group, -CN. The liquid nitrile is collected by simple distillation.
For example, you will get ethanenitrile by dehydrating ethanamide.
Note: This is a just a flow scheme rather than a proper equation. I haven't been able to find a single example of the use of the full equation for this reaction. In fact the phosphorus(V) oxide reacts with the water to produce mixtures of phosphorus-containing acids.
Making nitriles from aldehydes and ketones
Aldehydes and ketones undergo an addition reaction with hydrogen cyanide. The hydrogen cyanide adds across the carbon-oxygen double bond in the aldehyde or ketone to produce a hydroxynitrile. Hydroxynitriles used to be known as cyanohydrins.
For example, with ethanal (an aldehyde) you get 2-hydroxypropanenitrile:
With propanone (a ketone) you get 2-hydroxy-2-methylpropanenitrile:
In every example of this kind, the -OH group will be on the number 2 carbon atom - the one next to the -CN group.
The reaction isn't normally done using hydrogen cyanide itself, because this is an extremely poisonous gas. Instead, the aldehyde or ketone is mixed with a solution of sodium or potassium cyanide in water to which a little sulphuric acid has been added. The pH of the solution is adjusted to about 4 - 5, because this gives the fastest reaction. The reaction happens at room temperature.
The solution will contain hydrogen cyanide (from the reaction between the sodium or potassium cyanide and the sulphuric acid), but still contains some free cyanide ions. This is important for the mechanism.
Note: If you want the mechanism for this reaction, you will find it explained if you follow this link.
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These are useful reactions because they not only increase the number of carbon atoms in a chain, but also introduce another reactive group as well as the -CN group. The -OH group behaves just like the -OH group in any alcohol with a similar structure.
For example, starting from a hydroxynitrile made from an aldehyde, you can quite easily produce relatively complicated molecules like 2-amino acids - the amino acids which are used to construct proteins.
Note: The first step is the replacement of -OH in an alcohol by chlorine.
The second step is the reaction between a halogenoalkane and ammonia.
The final step is hydrolysis of a nitrile.
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6 komentar:
11 Juni 2012 pukul 20.42
hy via,
do you know about Applications of nitrile rubber? based on the information I got Nitrile rubber is also referred to as also Nitrile butadiene rubber, or "NBR". The products are used in several industries because the general properties of NBR are not altered by minor structural/compositional differences.
The major uses for Nitrile rubber are in the healthcare industry and the automobile industry because the gloves are resistant to many solvents.
The nitrile gloves gloves are resistant to oil, fuel, and other chemicals.
In the healthcare industry, Nitrile gloves are used as an alternative to Latex gloves because some people experience allergic reactions to Latex gloves.
do you have different answer or another answer?
thank's
11 Juni 2012 pukul 22.06
beside use in the healthcare industry and the automobile industry, nitrile rubber also use for automotive transmission belts, hoses, O rings, gaskets, oil seals, V belts, synthetic leather, printer's roller, and as cable jacketing.
Nitrile butadiene is also used to create moulded goods, footwear, adhesives, sealants, sponge, expanded foams, and floor mats. Nitrile rubber is more resistant than natural rubber to oils and acids, but has inferior strength and flexibility. Nitrile gloves are nonetheless three times more puncture-resistant than rubber gloves.
12 Juni 2012 pukul 09.01
hi viaa...
thx for your information about nitriles.. we know The nitrile functional group is found in several drugs., so< can u give example the structure for it,, thx
12 Juni 2012 pukul 11.19
There are other The uses of nitrile rubber include non-latex gloves for the healthcare industry, automotive transmission belts, hoses, O rings, gaskets, oil seals, V belts, synthetic leather, printer's roller, and as cable jacketing; NBR latex can also be used in the preparation of adhesives and as a pigment binder.
Unlike polymers meant for ingestion, where small inconsistencies in chemical composition/structure can have a pronounced effect on the body, the general properties of NBR are not altered by minor structural/compositional differences. The production process itself is not overly complex; the polymerization, monomer recovery, and coagulation processes require some additives and equipment, but they are typical of the production of most rubbers. The necessary apparatus is simple and easy to obtain. For these reasons, the substance is widely produced in poorer countries where labor is relatively cheap. Among the highest producers of NBR are mainland China and Taiwan.
A hydrogenated version of nitrile rubber, HNBR, also known as HSN (highly saturated nitrile) is commonly used to manufacture o-rings for automotive air-conditioning systems.[2]
In January 2008 the European Commission imposed fines totaling €34,230,000 on the Bayer and Zeon groups for fixing prices for nitrile butadiene rubber, in violation of the EU ban on cartels and restrictive business practices (Article 81 of the EC Treaty and Article 53 of the EEA Agreement).[3]
Criminals have also been known to wear these gloves during the commission of their crimes. These gloves are often chosen because of their tight, thin fit that allows the hands to remain dexterous. Ironically, because of the thinness of these gloves, fingerprints may actually pass through the material as glove prints, thus transferring the wearer's prints onto whatever surface is touched or handled.
For more complete please check : http://en.wikipedia.org/wiki/Nitrile_rubber,, http://wiki.answers.com/Q/Applications_of_nitrile_rubber. Thanks before elsa
12 Juni 2012 pukul 11.23
Tiara: Guys do you know dangerous of nitriles? Do not use these gloves when working with red fuming nitric acid, as sudden combustion of these two chemicals could cause serious chemical burns. Caution must be taken when working with the acid and the gloves at the same time.
12 Juni 2012 pukul 11.25
Citra: check this http://www.biopsychiatry.com/structures/index.html,there are much types of nitriles that content of drugs
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