hydroxyl group. Hydroxyl What is characteristic of the presence of a hydroxyl group
The reaction is called xanthogen test into primary and secondary hydroxyl groups. Primary and secondary alcohols in the presence of alkalis react with carbon disulfide, forming water-soluble salts of alkyl xanthates-1:
Salts of alkyl xanthates in reaction with solutions of bivalent copper salts give brown xanthates of cuprous copper:
Xanthates of tertiary alcohols are unstable and decompose to mineral compounds, as a result of which this reaction is unsuitable for the determination of tertiary alcohols.
Methodology: dissolves a drop of the test substance in 1 cm 3 of diethyl ether, add a drop of carbon disulfide and a few grains of caustic soda. The mixture, shaking in a test tube, is slightly heated in a water bath. A drop of a solution of 2% solution of CuSO 4 is added. If there is an alcohol group in the substance, a brown precipitate of copper xanthate precipitates. In the absence of hydroxyl groups, the color of the precipitate is blue.
Reaction to phenols
Most phenols give an intense color with a solution of iron (III) chloride.:
The usual color of the solution is blue or purple. But in a number of complex phenols, it is green or red. The reaction is carried out in aqueous solutions or in chloroform to distinguish phenols from enols . The latter give intense color in methanol or ethanol.
Methodology: in a test tube, dissolve several crystals or one drop of a substance in 1 cm 3 of water or chloroform. Shake, add 1 drop of 1% FeCl 3 aqueous solution. In the presence of phenolic hydroxide, an intense color immediately appears. Enols under these conditions give only a faint color. Phenols react more clearly in the presence of water.
Reaction to glycols and polyhydric alcohols
Most polyhydric alcohols containing hydroxyl groups at adjacent carbon atoms form chelated copper glycolates, soluble in water and colored bright blue:
Glycolates are stable in an alkaline environment, but decompose into the parent compounds (copper salts and glycols) in an acidic environment.
Methodology: 10 drops of a 3% solution of CuSO 4 and 1 cm 3 of 5% sodium hydroxide are poured into a test tube. Three drops of the test solution are added to the mixture. If it contains a polyhydric alcohol, the blue precipitate of freshly precipitated copper hydroxide dissolves and the solution takes on an intense blue color. -amino acids and -aminoalcohols behave in the same way.
carbonyl group
Reaction with hydroxylamine hydrochloride
The reaction of hydroxylamine with a sterically unhindered carbonyl group is also quite general:
Since hydroxylamine hydrochloride has an almost neutral reaction, and the resulting oxime is not a strong base, the course of the reaction can be easily controlled by increasing the acidity of the medium due to the release hydrogen chloride.
Methodology: to 2 cm 3 of 3% hydrochloric hydroxylamine in a test tube add a solution of 0.1 g of the test substance in 0.5 cm 3 of ethanol. Heat the mixture in a water bath. Add one drop of methyl orange indicator. If the test substance contains a carbonyl group, a distinct reddening of the indicator is observed. Reactions are hindered by carboxylic acids reacting with hydroxylamine. It is easy to verify their absence by checking the test solution for litmus. Instead of the indicated indicators, it is permissible to use universal indicator paper..
Sooner or later one has to deal with hydroxyl groups. First, let's define what it is? After all, hydroxyl OH is a part of many chemical compounds - alkalis, alcohols, even water, H + OH.
Hydroxyl is called an aqueous residue. Since this group has an unsaturated valency, it cannot exist independently, and the free state is not available to it. But she feels quite well in chemical reactions, where she reacts as a whole, easily passes from one compound to another, being its element. Let's take the same water. It can be considered as consisting of a hydrogen molecule and an H-OH hydroxyl residue.
Basic hydrates consist of a metal and one or more hydroxyl residues. In alcohols, the hydroxyl group replaces the hydrogen atoms in hydrocarbons. If a hydroxyl group is present in a chemical element, then certain properties are inherent in it. Take the same alcohols as a vivid example, familiar to everyone. Known ethyl, methyl and other alcohols have certain properties due to hydroxyls.
The alkaline properties of hydrates also depend on them. The formation of a stable hydroxyl ion OH "when decomposing in an aqueous solution will contribute to the acquisition of a negative charge by hydroxyl, while the metal will be positively charged. Therefore, a hydroxyl solution containing free hydroxyl ions will be alkaline.
In physiology, these properties of hydroxyls are used to accelerate the motility of spermatozoa or to restore their mobile function when they are completely inert. There is an opinion that blood clotting increases due to the breakdown of platelets, which manifests itself with increased alkalinity, and many other processes in the bodies of living organisms change.
Alcohols
Defining the concept of alcohols, we can say that these are organic substances containing one or more hydroxyl groups. The compound is a hydrocarbon group. Alcohols are distinguished by atomicity:
- monohydric - ethyl and methyl alcohols;
- diatomic or glycols - ethylene glycol, propanediol;
- triatomic - glycerin;
- polyatomic - those that contain from three hydroxyl groups in the composition of the molecule.
- limiting - they contain only limiting radicals;
- unsaturated - have multiple bonds between carbon atoms in the molecule;
- aromatic - contain, along with the hydroxyl group, a benzene ring and are linked by carbon atoms.
- phenols proper;
- naphthols having two condensed nuclei;
- anthrols - 3 cores;
- quadruple - phenantrols;
- benzotetrols - 5 cores.
Where are phenols found? In peat, wood, coal and oil workings. In nature, in the form of derivatives, they are found in plants (lignins, tannins, flavonoids, and others). In a free state, it can be found in lichens and in pine needles, cones. Pyrocatechin is found in grapefruit and onions, and phloroglucinol in the bark of apple and plum trees, in sequoia cones. Hydroquinone is found in pear leaves and seeds, while thymol is found in thyme leaves.
It should be noted that phenols have a strong specific odor. They are classified as weak acids.
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And inorganic compounds, in which the hydrogen and oxygen atoms are linked by a covalent bond. In organic chemistry, it is also called " alcohol group».
The oxygen atom determines the polarization of the alcohol molecule. The relative mobility of the hydrogen atom causes lower alcohols to enter into substitution reactions with alkali metals. In inorganic chemistry, they are part of bases, including alkalis.
Hydroxyl radical
Hydroxyl radical is a highly reactive and short-lived OH radical formed by the combination of oxygen and hydrogen atoms. It is usually formed during the breakdown of hydroperoxides, in atmospheric chemistry, by the interaction of excited oxygen molecules with water, or by the action of ionizing radiation.
Role in biology
The hydroxyl radical belongs to reactive oxygen species and is the most active component of oxidative stress. It is formed in the cell primarily by the reduction of hydrogen peroxide in the presence of a transition metal (such as iron). Half-life t 1/2 of the hydroxyl radical in vivo- very short - about 10 −9 s, which, together with its high reactivity, leads to the fact that it is one of the most dangerous agents formed in the body. Unlike superoxide, which can be detoxified by superoxide dismutase, there is no enzyme that eliminates the hydroxyl radical due to its too short lifetime to diffuse into the active site of the enzyme. The cell's only defense against this radical is high levels of low molecular weight antioxidants, such as glutathione. The resulting hydroxyl radical instantly reacts with any oxidizable molecule in the immediate environment. Of the most biologically important components of the cell, the hydroxyl radical is able to oxidize carbohydrates, nucleic acids (which can lead to gene mutation or damage), lipids (causing lipid peroxidation), and amino acids.
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An excerpt characterizing the Hydroxyl group
“And one more thing, please, my dear, sharpen my saber; blunt ... (but Petya was afraid to lie) she had never been honed. Can it be done?- Why, maybe.
Likhachev got up and rummaged through his packs, and Petya soon heard the warlike sound of steel on a bar. He climbed onto the wagon and sat on its edge. The Cossack sharpened his saber under the wagon.
- And what, the good fellows sleep? Petya said.
- Who is sleeping, and who is like this.
- Well, what about the boy?
- Is it spring? He was there, in the hallways, collapsed. Sleeping with fear. It was glad.
For a long time after that Petya was silent, listening to the sounds. Footsteps were heard in the darkness and a black figure appeared.
- What are you sharpening? the man asked, approaching the wagon.
- But the master sharpen his saber.
“It’s a good thing,” said the man, who seemed to be a hussar to Petya. - Do you have a cup left?
“At the wheel.
The hussar took the cup.
“It’s probably light soon,” he said, yawning, and went somewhere.
Petya should have known that he was in the forest, in the party of Denisov, a verst from the road, that he was sitting on a wagon recaptured from the French, near which the horses were tied, that the Cossack Likhachev was sitting under him and sharpening his saber, that a large black spot to the right - a guardhouse, and a bright red spot below to the left - a dying fire, that the man who came for a cup was a hussar who wanted to drink; but he knew nothing and did not want to know it. He was in a magical realm, in which there was nothing like reality. A big black spot, maybe it was definitely a guardhouse, or maybe there was a cave that led into the very depths of the earth. The red spot may have been fire, or perhaps the eye of a huge monster. Maybe he’s definitely sitting on a wagon now, but it’s very possible that he’s not sitting on a wagon, but on a terribly high tower, from which if you fall, you would fly to the ground all day, a whole month - all fly and you will never reach . It may be that just the Cossack Likhachev is sitting under the wagon, or it may very well be that this is the kindest, bravest, most wonderful, most excellent person in the world, whom no one knows. Perhaps it was the hussar who was exactly passing for water and went into the hollow, or perhaps he had just disappeared from sight and completely disappeared, and he was not there.
Whatever Petya saw now, nothing would surprise him. He was in a magical realm where anything was possible.
He looked up at the sky. And the sky was as magical as the earth. The sky was clearing, and over the tops of the trees clouds quickly ran, as if revealing the stars. Sometimes it seemed that the sky was clearing and showed a black, clear sky. Sometimes it seemed that these black spots were clouds. Sometimes it seemed that the sky was high, high above the head; sometimes the sky descended completely, so that you could reach it with your hand.
Functional groups are formed by atoms or groups of atoms that replace a hydrogen atom in a carbon base.
Functional groups have common chemical properties that belong to the same class of hydrocarbon derivatives, which makes it easier to classify the properties of compounds (for example, alcohols have common properties) and facilitates the study of all organic chemistry.
It must be admitted that the presence of several functional groups in a molecule greatly complicates the situation, since such molecules can participate in a very large number of chemical reactions - there's nothing to be done - organic chemistry is a rather complicated science.
Alcohols: R-OH
Alcohols are derivatives of saturated and unsaturated hydrocarbons, in the molecules of which the hydrogen atom (atoms) are replaced by a hydroxyl group (groups) -OH, which determines the general properties of all alcohols. For this reason, in many cases it does not matter what the rest of the alcohol molecule will be, because. the functional group determines the general behavior of alcohols in many chemical reactions.
Alcohols are usually denoted by the general formula R-OH(R is the rest of the molecule or hydrocarbon radical). Alcohol names end in a suffix -ol, which replaces the suffix -en in the name of the corresponding alkane.
methanol(methyl or wood alcohol) is obtained by a synthesis reaction from carbon monoxide and hydrogen in the presence of a catalyst at high pressures and temperatures:
CO (g) + 2H 2 (g) → CH 3 OH (l)
Methanol is used to produce formaldehyde. One of the promising directions is the use of methanol as a replacement for gasoline.
ethanol(ethyl or wine alcohol) is obtained from various sugary substances using a fermentation reaction caused by the action of enzymes that produce yeast fungi (this method of obtaining alcohol is used to prepare alcoholic beverages):
C 6 H 12 O 6 (solution) → 2CH 3 CH 2 OH (g) + 2CO 2 (g)
The second way to produce ethanol is synthesis from ethylene in the presence of catalysts (ethanol is used as a solvent in the perfume and pharmaceutical industries, as an additive to gasoline to increase the octane number):
H 2 C \u003d CH 2 + H 2 O → CH 3 -CH 2 -OH
Carboxylic acids: R-COOH
The functional group in carboxylic acids is the carboxyl group -COOH.
O || R-C-OH
The names of carboxylic acids end in -oic acid.
Carboxylic acids are produced using oxidation reactions alcohols. Below is the oxidation reaction of ethanol in air, which results in the formation of acetic (ethanoic) acid (do not leave an open bottle of wine for a long time):
CH 3 CH 2 OH (l) + O 2 (g) → CH 3 COOH (l) + H 2 O (l)
Many carboxylic acids have a strong unpleasant odor.
Esters: R-COO-R
The composition of esters is in many ways similar to carboxylic acids (the hydrogen atom in the functional group is replaced by the second group -R).
Esters are obtained from carboxylic acids when they react with alcohols ( esterification reaction), while, unlike carboxylic acids, the resulting esters have a pleasant smell (esters give the aroma to flowers, the smell of fruits and berries):
O O || || R-C-OH + H-O-R " → R-C-O-R" + H 2 O
Ethers: R-O-R
The ether functional group is represented by one oxygen atom bonded to two hydrocarbon groups.
Ethers are chemically quite inert and are used as solvents in organic reactions. Reacting (slowly) with atmospheric oxygen, ethers form peroxides, which are explosive compounds (it is for this reason that physicians have abandoned the use of diethyl ether as an anesthetic).
Get ethers using the reaction dehydration alcohols. For example, diethyl ether is synthesized by dehydration of ethyl alcohol in the presence of sulfuric acid:
2CH 3 CH 2 OH (l) → CH 3 CH 2 -O-CH 2 CH 3 (l) + H 2 O (l)
If you use two different alcohols, you get a mixed ether containing two different -R groups.
Aldehydes and ketones
The aldehyde functional group is a divalent carbonyl group bonded to one hydrogen atom and a hydrocarbon radical:
O || R-C-H
The ketone functional group is a divalent carbonyl group linked to two hydrocarbon radicals:
O || R-C-R"
Aldehydes and ketones are obtained from the oxidation of alcohols. Aldehydes, which have a benzene ring in their structure, are widely used in the perfume industry because they have a pleasant aroma. Formaldehyde(CH 2 =O) is used as an antiseptic, as well as in the synthesis of polymers for the production of phenol. The simplest ketone acetone(CH 3 -CO-CH 3) is a good organic solvent used in the paint industry.
Amides and amines
Functional group of amines:
Functional group of amides:
O || R-C-NH 2
Amides and amines are derivatives of ammonia, therefore, they are weak bases. They are widely used in the production of synthetic dyes, medicines, plastics, explosives.
Hydroxyl group in alcohols
Hydroxyl group is a functional group OH of organic and inorganic compounds in which hydrogen and oxygen atoms are linked by a covalent bond. In organic chemistry, it is also called the "alcohol group".
The oxygen atom determines the polarization of the alcohol molecule. The relative mobility of the hydrogen atom leads to the fact that lower alcohols enter into substitution reactions with alkali metals. In inorganic chemistry, they are part of bases, including alkalis.
Hydroxyl radical
The hydroxyl radical is a highly reactive and short-lived OH radical formed by the combination of oxygen and hydrogen atoms. It is usually formed by the breakdown of hydroperoxides, in atmospheric chemistry, by the interaction of excited oxygen molecules with water, or by the action of ionizing radiation.
Role in biology
The hydroxyl radical belongs to reactive oxygen species and is the most active component of oxidative stress. It is formed in the cell mainly during the reduction of hydrogen peroxide in the presence of a transition metal. The half-life t 1/2 of the hydroxyl radical in vivo is very short - about 10 s, which, together with its high reactivity, leads to the fact that it is one of the most dangerous agents formed in the body. Unlike superoxide, which can be detoxified by superoxide dismutase, there is no enzyme that eliminates the hydroxyl radical due to its too short lifetime to diffuse into the active site of the enzyme. The cell's only defense against this radical is high levels of low molecular weight antioxidants such as glutathione. The resulting hydroxyl radical instantly reacts with any oxidizable molecule in the immediate environment. Of the most biologically important components of the cell, the hydroxyl radical is able to oxidize carbohydrates, nucleic acids, lipids, and amino acids.
