Oxalic Acid: Preparation, Properties & Uses |

Oxalic Acid.

It occurs every bit potassium hydrogen oxalate inwards the woods sorrel, rhubarb, together with tomatoes. The insoluble calcium oxalate is constitute inwards roughly stony deposits inwards kidneys together with bladder inwards the human body.

Preparation of Oxalic Acid.

(1) Manufacture. Oxalic acid is made industrially past times heating sodium formate to 400°C.

The sodium oxalate thence formed is dissolved inwards H2O together with calcium hydroxide added to precipitate calcium oxalate. The solution is filtered together with the filtrate treated amongst the calculated quantity of dilute sulphuric acid to divulge the oxalic acid.

Calcium sulphate precipitates, together with oxalic acid is crystallised from the filtrate every bit the hydrate, COOH)2.2H2O

Laboratory Method of Oxalic Acid. In the laboratory, oxalic acid is made past times oxidation of sucrose or molasses amongst concentrated nitric acid inwards the presence of vanadium pentoxide every bit a catalyst.

The -CHOH.CHOH- units acquaint inwards sucrose molecule are split upwardly out together with oxidised to oxalic acid.

Properties of Oxalic Acid.

Physical Properties of Oxalic Acid. When crystallised from water, colourless prismatic crystals of oxalic acid dihydrate, (COOH)2. 2H2O, are obtained. The dihydrate melts at 101.5°C, piece the anhydrous acid melts at 189.5°C. The hydrate acid becomes anhydrous when carefully heated to 150°C. Oxalic acid is an active poison, depressing the key nervous organisation together with causing malfunction of kidneys.

Chemical Properties of Oxalic Acid. The oxalic acid molecule is made of 2 carboxyl groups inwards the straight off union. It gives all the commons reactions of COOH grouping twice. Also, the acid gives roughly peculiar reactions which postulate the cleavage of the weakened linkage betwixt the 2 highly oxidised carbon atoms.

(1) Formation of Mono-and Di-derivatives. Oxalic acid is a much stronger acid than acetic acid together with readily forms 2 serial of salts, esters, acid halides together with amides.

(2) The activity of Heat. When heated at 150C, it decarboxylates to reach formic acid.

(3) Action amongst Glycerol. Oxalic acid reacts amongst glycerol to cast formic acid or allyl alcohol, depending upon experimental conditions.
(4) Action amongst H2SO4. When heated amongst concentrated sulphuric acid, it is decomposed to reach carbon dioxide, carbon monoxide together with water.

(5) Oxidation. It is readily oxidised, for illustration amongst acidified potassium permanganate.

Oxalic Acid Uses.

Uses of oxalic acid.

1. For removing ink stains together with for bleaching straw for hats, since it reduces chocolate-brown ferric compounds to soluble together with close colourless ferrous salts.
2. As a mordant inwards dyeing together with calico printing.
3. In the industry of inks together with metallic polishes.
4. For preparing allyl alcohol together with formic acid inwards the laboratory.
5. In redox Titrations.

Tartaric Acid | Uses, Preparation, & Properties |

Tartaric Acid.

Tartaric acid occurs gratis too equally potassium hydrogen tartarate inwards grape juice.

Properties of tartaric acid.

Preparation from grape juice. Argol which is potassium hydrogen tartarate (Cream of tartar), is formed equally a  sludgy precipitate during the fermentation of grape juice inwards vino making . It is dissolved inwards boiling H2O too neutralised amongst milk-of-lime. Calcium tartarate is precipitated, land potassium tartarate remains inwards solution. The calcium tartarate is separated past times filtration too the filtrate treated amongst calcium chloride when potassium tartarate is too precipitated equally calcium tartarate.

The calcium tartarate obtained inwards the ii steps is treated amongst a calculated quantity of dilute H2SO4 to loose tartaric acid. The calcium sulphate precipitate that is formed is removed past times filtration, too the filtrate concentrated past times evaporation to larn the crystals of tartaric acid.

Preparation from maleic acid. Maleic acid produced industrially past times oxidation of cyclohexane is treated amongst element of group I KMnO4 to larn meso-tartaric acid.

Similarly, fumaric acid yields racemic tartaric acid.

Tartaric Acid properties.

Physical properties of tartaric acid. Tartaric acid is a white crystalline substance, mp 171 °C, having acidic taste. It is soluble inwards H2O too alcohol, only sparingly therefore inwards ether. Since it has ii asymmetric carbon atoms, tartaric acid shows optical isomerism. The natural tartaric acid is the dextro variety, α =+ 12.7.

Chemical properties of tartaric acid. Tartaric acid molecule has ii secondary alcohol groups (>CHOH) too ii -COOH groups, too behaves accordingly.

Formation of salts. It forms ii serial of salts when treated amongst alkalis.

Action of heat. When heated, tartaric acid converted to pyruvic acid.

However, on rigid heating, tartaric acid chars, giving aroma of burnt sugar. (test)

Reaction amongst HBr. It reacts amongst hydrobromic acid to shape 2.3-dibromosuccinic acid.

Reduction. When heated amongst Hl, tartaric acid is reduced to malic acid too then succinic acid.

Oxidation. (i) On oxidation amongst HNO3 it is converted to tartonic acid too and then oxalic acid.

(ii) When warmed amongst ammoniacal silvery nitrate, tartaric acid is oxidation to tartonic acid too silvery mirror is formed . (test)

(iii) Fenton's reagent (Fe³⁺/H₂O₂) oxidises tartaric acid to dihydroxymaleic acid.

(6) Formation of complexes. In fehling solution ( CuSO₄ + sodium potassium + NaOH) the soluble copper hydroxide get-go formed dissolves due to the formation of a soluble complex,

Tartaric acid uses.

Tartaric acid is used.

1. In carbonate beverages too effervescent tablets.
2. In backing powder.
3. As mordant.
4. In silvering of mirrors.
5. In tanning.
6. For preparing tartar emetic, cream of tartar, Rochelle common salt etc.

Citral | Uses, Structure, Preparation, & Properties |

Citral.

It is the most of import acyclic (open chain) monoterpenoid too has the structural formula.

Citral occurs to the extent of eighty per cent inwards lemon grass oil. It is likewise acquaint inwards the crude oil of citrus fruits (citron, orange, lemon)

Preparation of Citral.

It is obtained from lemon grass crude oil past times handling amongst sodium bisulphite solution. Crystalline citral bisulphite derivative separates. This upon hydrolysis amongst sodium carbonate gives pure citral.

Properties of Citral.

Citral is a colourless liquid, bp 224-228°C. It has a potent lemon-like odour. It exhibits geometrical isomerism close the double-bonded carbons carrying CH3 and CHO groups. This cis-isomer is known equally citral-a too the trans-isomer citral-b. Ordinary citral obtained from lemon grass crude oil is, inwards fact, a mixture of citral-α (90%) too citral-b (10%).

Citral Uses.

Citral is used extensively inwards the perfume too flavor manufacture to copy lemon-like odour, too for the manufacture of vitamin A. Recently citral has expire of import equally a drug for reducing blood pressure.

Citral Structure.

Element analysis too molecular weight determinations exhibit that the molecular formula of citral is C10H16O.

Presence of teo C=C. It adds 2 molecules of bromine to shape a tetrabromide, indicating the presence of 2 carbon-carbon double bonds.

Presence of CHO. It forms an oxime too on oxidation gives geranic acid without loss of whatever carbon atom.

Carbon skeleton. Simmler (1891) suggested that 2 isoprene units are joined head-to-tail inwards citral (Isoprene rule), too its carbon skeleton was.

Position of C=C bonds indicated. The oxidation of citral amongst alkaline metal permanganate, followed past times chromic acid, gives acetone, levulinic acid, too oxalic acid. This is accountable exclusively if the set of the double bonds is equally shown inwards the formula below.

Position of double bonds confirmed. The inwards a higher house construction of citral is supported past times the decomposition of citral amongst aqueous Na2CO3 to hand methylheptenone too acetaldehyde.

Synthesis. Structure of citral was confirmed past times the next synthesis from methylheptenone. The diverse steps are

1. Reformatsky reaction.
2. Hydrolysis amongst dilute acid.
3. Dehydration amongst acetic anhydride.
4. Distilling calcium geranate amongst calcium formate.

Urea | Uses, Structure, Preparation, & Properties |

Urea.

It is the normal terminate production of the human metabolism of nitrogen-containing foods (proteins). An adult somebody excretes almost iii grams of urea inwards urine inwards 24 hours.

Preparation of urea.

(1) Urea is made commercially past times the reaction of liquid ammonia together with carbon dioxide at 150-200°C together with almost 200 atmospheres pressure. Ammonium carbamate outset formed decomposes to shape urea.

(2) It tin hold upward prepared inwards the laboratory past times the activity of ammonia on carbonyl chloride.

(3) Wohler was the outset to synthesise urea inwards 1828 past times evaporating a solution of ammonium

cyanate. This method is of historical involvement only.

Properties of Urea.

Physical Properties.

Urea is a colorless, crystalline solid, mp 135°C. It is real soluble inwards H2O giving neutral solutions. It is less soluble inwards alcohol together with insoluble inwards ether, chloroform, together with benzene.

Chemical Properties.

Urea contains an amide grouping attached to an amino grouping together with gives reactions of both these functions. It may hold upward idea of equally having 2 amide groups alongside a mutual - CO- function.

Thus it behaves equally a diamide inwards most reactions.

Some of the reactions of urea are listed below.

(1) Salt Formation. Urea is a feeble mono acid-base (K_b= 1.5 x 10^-14). Thus it reacts alongside concentrated nitric acid together with oxalic acid to shape salts.

The inwards a higher house salts comprise the oxygen-protonated cation, [HOC(NH₂)₂]⁺, which is resonance-stabilized.

(2) Hydrolysis. Like other amides, urea is hydrolysed nether both acidic or element of group I weather condition to

give ammonia together with carbon dioxide.

An enzyme called urease, acquaint inwards reason together with soya edible bean hydrolyzes urea to ammonium carbonate. This reaction is used for the quantitative estimation of urea.

(3) Reaction with HNO₂. Urea, similar other amides, reacts alongside nitrous acid when nitrogen is evolved, leaving the carbonic acid behind. This is plough decomposes to carbon dioxide together with water.

(4) Reaction alongside Alkaline Hypohalites. Urea is oidised to nitrogen when it is heated alongside excess of element of group I hypochlorite or hypobromite (Br₂+NaOH).

This reaction is too used to gauge urea past times mensuration the book of nitrogen envolved from a exam sample.

(5) Acetylation. Urea reacts alongside acylating agents e.g., acetyl chloride to shape N-acyl ureas or 'ureides'.

(6) Action of Heat. (a) On heating at 132°C, urea melts.Then the liquid on gentle heating at a slightly higher temperature decomposes, liberating ammonia together with leaving behind a solid chemical compound known equally Biuret.

Urea tin hold upward identified past times the Biuret Test. The meat is heated, a picayune inwards a higher house its melting point, inwards a dry out test-tube. Biuret is formed alongside the development of ammonia. When the development of ammonia begins to slacken, the balance is dissolved inwards H2O together with treated alongside a few drops of sodium hydroxide solution. To the solution is together with thence added a driblet of copper sulfate solution, when a purplish coloration is produced.

(b) When heated rapidly good inwards a higher house its melting point, urea is decomposed to isocyanic acid which trimerizes to cyanuric acid.

(7) Reaction alongside Hydrazine. Urea reacts alongside hydrazine at 100°C to shape semicarbazide.

Urea uses.

Urea is used.

1. Chiefly equally fertilizer.
2. As brute feed.
3. For making barbiturates.
4. for the industry of urea-formaldehyde resins.
5. As a stabilizer for explosives (nitrocellulose).

Urea Structure.

(1) By elemental analysis together with molecular weight determination, its molecular formula has been constitute to be CON₂H₄.

(2) Diamide formula. Its formation from carbonyl chloride together with ammonia indicates that urea has a symmetrical diamide formula.

The diamide formula is confirmed because of urea : (a) upon hydrolysis forms 2 molecules of

ammonia (b) alongside nitrous acid it liberates 2 molecules of N₂.

(3) Facts against the Diamide formula. It fails to explicate :

(a) Urea forms salts alongside acids similar HCl or HNO₃ land elementary amides gain not.

(b) It forms mono-salts entirely e.g., CO(NH₂)₂. HCl, showing that the molecule is unsymmetrical.

(4) Tautomeric Structure Proposed. To explicate the facts listed inwards (3), Chattaway proposed that urea

exists equally a tautomeric mixture.

It is the basic imide shape which forms a tabular array salt alongside a monobasic acid at the imide grouping (= NH.HCI).

(5) Resonance Structures. Urea is to a greater extent than stable than could hold upward expected of whatever carbonic acid derivative. In damage of the modern resonance theory, this stability of urea is attributed to its beingness equally a resonance hybrid.

(6) Formation of Mono-Salts Explained. The oxygen atom of the carbonyl grouping of urea is capable of coordinating alongside 1 proton (H⁺). The resulting cation is resonance stabilized past times considerable delocalization of the cationic charge.

Thus urea tin shape mono-salt alongside an acid similar HCl.

X-ray diffraction studies convey confirmed that inwards the crystalline tabular array salt of urea alongside HCl is acquaint an oxonium type cation equally shown above.

Formic Acid : Preparation, Properties, Uses

Formic Acid.

Formic acid derives its cite from the fact that it was kickoff obtained past times distillation of ants (Latin, Formica =ant):

Preparation. Formic acid may hold upward obtained every bit follows:

(1) From Methanol. By the oxidation of methanol amongst acidified sodium dichromate solution.

(2) From Oxalic Acid. Formic acid is prepared inwards the laboratory past times heating oxalic acid amongst glycerol catalyst at 110°C.

Laboratory Method.

Anhydrous glycerol (50 ml) as well as powdered oxalic acid (40 g) are placed inwards a flask as well as the apparatus laid upward every bit shown inwards Fig. 1.1 The flask is heated at 1 C till the development of carbon dioxide (marked past times effervescence) ceases. The reaction flask is so cooled as well as a fresh lot of oxalic acid (40 g) is added. The mixture is in ane trial again heated at 110°C when an aqueous solution of formic acid collects inwards the receiver.

The aqueous formic acid is neutralised amongst Pb carbonate. The solution of Pb formate therefore produced is filtered as well as concentrated. The crystals of Pb formate are so charged inwards the inner underground of a water-condenser as well as the apparatus laid upward every bit shown inwards Fig. 1.2. Hydrogen sulphide is allowed to transcend through the condenser spell steam is passed through its outer jacket. The anhydrous formic acid collecting inwards the receiver flask is freed from dissolved hydrogen sulphide past times distilling over fresh Pb formate.

Anhydrous formic acid may likewise hold upward made inwards the laboratory past times distilling a mixture of sodium formate as well as sodium hydrogen sulphate.

(3) From Carbon Monoxide. Formic acid is prepared industrially past times beating carbon monoxide.

with sodium hydroxide at 150°C as well as nether the pressure level of 8 atmospheres.

The complimentary acid is liberated from its sodium tabular array salt past times reaction amongst sulphuric acid.

Physical properties.

Formic acid is a colourless, abrupt smelling, irritating liquid, bp 100.8°C. It is miscible amongst water, ethanol, as well as there. It is really corrosive as well as causes bumps as well as blisters on the skin.

Chemical Properties.

Formic acid is unique because it contains both an aldehyde grouping as well as a carboxyl group.

Uses. 

Formic acid is used :

1. In stuff dyeing as well as finishing.
2. As a coagulating agent for security latex.
3. In leather tanning.
4. In the preservation of fruits.
5. As an antiseptic.
6. In the handling of gout.
7. In the laboratory training of carbon monoxide.