chemistry of organic compounds
TRANSCRIPT
Chemistry of Organic Compounds
• Chloroform
• Ethyl Alcohol
• Acetone
• Acetic anhydride
• Formaldehyde
• Polyethylene
Chloroform
• Formyl trichloride, Methane trichloride, Methyl trichloride, Methenyl trichloride
Chloroform-Properties• Molecular Formula
• Molar Mass
• Appearance
• Density
• Melting Point
• Boiling Point
• Molecular shape
• CHCl3• 119.38 g/mol
• Colourless liquid
• 1.483 g/cc
• -63.5 oC
• 61.2 oC
• Tetrahedral
Chlorofom • Chloroform (also known as trichloromethane and
methyl trichloride) is a chemical compound with formula CHCl3.
• It is a colorless liquid with a pleasant, nonirritating odor and a slightly sweet taste.
• It does not support combustion in air, although it will burn when mixed with more flammable substances.
• It is a member of a subset of environmental pollutants known as trihalomethanes, a by-product of chlorination of drinking water and a long-standing health concern.
Chloroform-history Chloroform was first produced independently and
simultaneously in 1831 by Justus von Liebig and the French chemist Eugene Soubeiran , who produced chloroform through the action of chlorine bleach powder (calcium hypochlorite) upon acetone (2-propanone) or ethanol (an application of the generic process known as the haloform reaction).
• In 1847, the Edinburgh obstetrician, James Young Simpson first used chloroform to effect general anesthesia during childbirth.
• The use of chloroform during surgery expanded rapidly thereafter, especially in Europe.
Chloroform-Production• Industrially, chloroform is produced by heating a mixture of chlorine
and either chloromethane or methane to 400-500°C. • At this temperature, a series of chemical reactions occur, converting
the methane or chloromethane to progressively more chlorinated compounds.
• CH4 + Cl2 → CH3Cl + HCl
• CH3Cl + Cl2 → CH2Cl2 + HCl
• CH2Cl2 +Cl2 → CHCl3 + HCl
• CHCl3 + Cl2 → CCl4 + HCl • The output of this process is a mixture of the four chloromethanes,
chloromethane, dichloromethane, chloroform (trichloromethane), and tetrachloromethane, which are then separated by distillation.
Chloroform-uses• In the late 19th and early 20th centuries, chloroform was
used as an inhaled anesthetic during surgery. However, safer, more flexible drugs have entirely replaced it in this role. The major use of chloroform today is in the production of the freon refrigerant R-22. However,, this use can be expected to decline as R-22 is replaced by refrigerants that are less liable to result in ozone depletion.
• Smaller amounts of chloroform are used as a solvent in the pharmaceutical industry, and for producing dyes and pesticides.
• Chloroform is often used as a tool in kidnapping, especially in books and movies.
• Chloroform containing deuterium (heavy hydrogen), CDCl3, is the most common solvent used in Nuclear Magnetic Resonance (NMR) spectroscopy.
Chloroform-safety• As might be expected from its use as an anesthetic,
inhaling chloroform vapors depresses the central nervous system. Breathing about 900 ppm for a short time can cause dizziness, fatigue, and headache.
• Chloroform once appeared in toothpastes, cough syrups, ointments, and other pharmaceuticals, but it has been banned in consumer products.
Ethyl Alcohol - Ethanol• Ethanol
Ethyl Alcohol-other names
• Ethyl alcohol;
• Grain alcohol;
• Pure alcohol;
• Hydroxyethane;
• Drinking alcohol;
• Ethyl hydrate;
• Absolute alcohol
Ethyl Alcohol
• Molecular Formula• Molar Mass• Appearance• Density• Melting Point• Boiling Point
• C2H5OH
• 46.07 g/cc• Colourless liquid• 0.789 g/cc• -114.3 C• 78.4 C
Ethyl Alcohol
• Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid.
• It is a powerful psychoactive drug and one of the oldest recreational drugs.
• It is best known as the type of alcohol found in alcoholic beverages.
• In common usage, it is often referred to simply as alcohol or spirits.
Ethyl alcohol• Ethanol is a straight-chain alcohol, and its molecular
formula is C2H5OH.
• Its empirical formula is C2H6O.
• An alternative notation is CH3–CH2–OH, which indicates that the carbon of a methyl group (CH3–) is attached to the carbon of a methylene group (–CH2–), which is attached to the oxygen of a hydroxyl group (–OH).
• It is a constitutional isomer of dimethyl ether.
• Ethanol is often abbreviated as EtOH, using the common organic chemistry notation of representing the ethyl
group (C2H5) with Et.
Ethyl Alcohol• The fermentation of sugar into ethanol is one of the
earliest organic reactions employed by humanity. • The intoxicating effects of ethanol consumption have
been known since ancient times. • In modern times, ethanol intended for industrial use is
also produced from by-products of petroleum refining.• Ethanol has widespread use as a solvent of substances
intended for human contact or consumption, including scents, flavorings, colorings, and medicines.
• In chemistry, it is both an essential solvent and a feedstock for the synthesis of other products.
• It has a long history as a fuel for heat and light, and more recently as a fuel for internal combustion engines.
Ethyl Alcohol• Ethanol is a volatile, colorless liquid that has
a strong characteristic odor. It burns with a
smokeless blue flame that is not always visible
in normal light. Ethanol is a versatile solvent, miscible with water
and with many organic solvents, including
acetic acid, acetone, benzene, carbon tetrachloride,
chloroform, diethyl ether, ethylene glycol, glycerol, nitromethane, pyridine, and toluene.
It is also miscible with light aliphatic hydrocarbons, such as pentane and hexane, and with aliphatic chlorides such as trichloroethane and tetrachloroethylene.
Ethyl alcohol-production• Ethanol is produced both as a petrochemical, through the hydration
of ethylene, and biologically, by fermenting sugars with yeast. Which process is more economical is dependent upon the prevailing prices of petroleum and of grain feed stocks.
• Ethylene hydration • Ethanol for use as an industrial feedstock or solvent is often made
from petrochemical feed stocks, primarily by the acid-catalyzed hydration of ethylene, represented by the chemical equation– C2H4(g) + H2O(g) → CH3CH2OH(l).
Ethyl alcohol-production• Ethanol for use in alcoholic beverages, and the vast majority of
ethanol for use as fuel, is produced by fermentation. When certain species of yeast metabolize sugar they produce ethanol and carbon dioxide. The chemical equation below summarizes the conversion:
• C6H12O6 → 2 CH3CH2OH + 2 CO2.
• The process of culturing yeast under conditions to produce alcohol is called fermentation. This process is carried out at around 35–40 °C.
• To produce ethanol from starchy materials such as cereal grains, the starch must first be converted into sugars. In brewing beer, this has traditionally been accomplished by allowing the grain to germinate, or malt, which produces the enzyme amylase. When the malted grain is mashed, the amylase converts the remaining starches into sugars.
Grades of ethanol• Denatured alcohol- • Absolute Ethanol- Absolute or anhydrous alcohol refers to ethanol
with a low water content. Absolute ethanol is used as a solvent for laboratory and industrial applications.
• Rectified spirits - Rectified spirit, an azeotropic composition containing 4% water, is used instead of anhydrous ethanol for various purposes.
Reactions of ethanol• Ethanol is classified as a primary alcohol, meaning that the carbon
to which its hydroxyl group is attached has at least two hydrogen atoms attached to it as well. Many of the reactions of ethanol occur at its hydroxyl group.
• Ester formation: In the presence of acid catalysts, ethanol reacts with carboxylic acids to produce ethyl esters and water:
RCOOH + HOCH2CH3 → RCOOCH2CH3 + H2O• This reaction, which is conducted on large scale industrially,
requires the removal of the water from the reaction mixture as it is formed.
• Dehydration: Strong acid desiccants cause the dehydration of ethanol to form diethyl ether and other byproducts.
• 2 CH3CH2OH → CH3CH2OCH2CH3 + H2O (on 120 °C)
Reactions of ethanol• Combustion: Complete combustion of ethanol forms carbon
dioxide and water– C2H5OH + 3 O2 → 2 CO2 + 3 H2O(l);– (ΔHc = −1371 kJ/mol) specific heat = 2.44 kJ/(kg·K)
• Acid-base chemistry• Ethanol is a neutral molecule and the pH of a solution of ethanol in
water is nearly 7.00. Ethanol can be quantitatively converted to its conjugate base, the ethoxide ion (CH3CH2O−), by reaction with an alkali metal such as sodium:– 2 CH3CH2OH + 2 Na → 2 CH3CH2ONa + H2
• or a very strong base such as sodium hydride– CH3CH2OH + NaH → CH3CH2ONa + H2
• The acidity of water and ethanol are nearly the same, as indicated by their pKa of 15.7 and 16 respectively. Thus, sodium ethoxide and sodium hydroxide exist in an equilbrium that is closely balanced:– CH3CH2OH + NaOH CH3CH2ONa + H2O
Reactions of ethanol• Halogenation• Ethanol reacts with hydrogen halides to produce
ethyl halides such as ethyl chloride and ethyl bromide via an sn2 reaction:– CH3CH2OH + HCl → CH3CH2Cl + H2O
• These reactions require a catalyst such as zinc chloride. HBr requires refluxing with a sulfuric acid catalyst.
• CH3CH2OH + SOCl2 → CH3CH2Cl + SO2 + HCl
• Upon treament with halogens in the presence of base, ethanol gives the corresponding haloform (CHX3, where X = Cl, Br, I).
Acetone• Acetone
Acetone- other names
• β-ketopropane,
• Dimethyl ketone,
• Dimethylformaldehyde,
• DMK, propanone,
• 2-propanone,
• Propan-2-one
Acetone-Properties
• Molecular Formula• Molar Mass• Appearance• Density• Melting Point• Boiling Point• Molecular shape
• C3H6O
• 58.08 g/ mol• Colourless liquid• 0.7925 g/cc• −94.9 °C, • 56.53 °C, • trigonal planar at C=O
Acetone• Acetone is the organic compound with the
formula (CH3)2CO.
• This colorless, mobile, flammable liquid is the simplest example of the ketones.
• Acetone is miscible with water and serves as an important solvent in its own right, typically as the solvent of choice for cleaning purposes in the laboratory.
Acetone -Production• Acetone is produced directly or indirectly
from propylene.
• Most commonly, in the cumene process, benzene is alkylated with propene and the resulting cumene (isopropylbenzene) is oxidized to give phenol and acetone:– C6H5CH(CH3)2 + O2 → C6H5OH + (CH3)2CO.
• Acetone is also produced by the direct oxidation of propene with a Pd(II)/Cu(II) catalyst, akin to the Wacker process.
Acetone uses• About half of the world's production of acetone is
consumed as a precursor to methyl methacrylate. • This application begins with the initial conversion of
acetone to its cyanohydrin:– (CH3)2CO + HCN → (CH3)2C(OH)CN
• In a subsequent step, the nitrile is hydrolyzed to the unsaturated amide, which is esterified:– (CH3)2C(OH)CN + CH3OH → CH2=(CH3)CCO2CH3 + NH3
• The second major use of acetone entails its condensation with phenol to give bisphenol A:– (CH3)2CO + 2 C6H5OH → (CH3)2C(C6H4OH)2 + H2O
• Bisphenol-A is a component of many polymers such as polycarbonates, polyurethanes, and epoxy resins.
Acetone-as solvent • Acetone is a good solvent for most plastics and synthetic fibres
including those used in laboratory bottles made of polystyrene, Polycarbonate and some types of polypropylene.
• It is ideal for thinning fiberglass resin, cleaning fiberglass tools and dissolving two-part epoxies and superglue before hardening.
• It is used as a volatile component of some paints and varnishes. • As a heavy-duty degreaser, it is useful in the preparation of metal
prior to painting; it also thins polyester resins, vinyl and adhesives.• Many millions of kilograms of acetone are consumed in the
production of the solvents methyl isobutyl alcohol and methyl isobutyl ketone. These products arise via an initial aldol condensation to give diacetone alcohol.
2 (CH3)2CO → (CH3)2C(OH)CH2C(O)CH3• Acetone is used as a solvent by the pharmaceutical industry and as
a denaturation agent in denatured alcohol. • Acetone is also present as an excipient in some pharmaceutical
products.
Acetic anhydrideAcetic anhydride
Acetic anhydride-Properties
• Molecular Formula• Molar Mass• Appearance• Density• Melting Point• Boiling Point
• C4H6O3
• 102.09 g/mol • Clear liquid• 1.082 g/cm3 • -73. oC• 139.8 oC
Acetic anhydride
• Acetic anhydride, or ethanoic anhydride, is the chemical compound with the formula (CH3CO)2O.
• Commonly abbreviated Ac2O, it is the simplest isolatable acid anhydride and is a widely used reagent in organic synthesis.
• It is a colorless liquid that smells strongly of acetic acid, formed by its reaction with the moisture in the air.
Acetic anhydride-structure• Acetic anhydride, like many other acid anhydrides that
are free to rotate, has experimentally been found to be aplanar.
• The pi system linkage through the central oxygen offers very weak resonance stabilisation compared to the dipole-dipole repulsion between the two carbonyl oxygens.
• Like most acid anhydrides, the carbonyl carbon of acetic anhydride is a potent electrophile as the leaving group for each carbonyl carbon (a carboxylate) is a good
electron-withdrawing leaving group.
Acetic anhydride• Acetic anhydride is produced by carbonylation of methyl
acetate– CH3CO2CH3 + CO → (CH3CO)2O
• This process involves the conversion of methyl acetate to methyl iodide and an acetate salt. Carbonylation of the methyl iodide in turn affords acetyl iodide, which reacts with acetate salts or acetic acid to give the product. Rhodium and lithium iodides are employed as catalysts. Because acetic anhydride is not stable in water, the conversion is conducted under anhydrous conditions. In contrast, the Monsanto acetic acid process, which also involves a rhodium catalyzed carbonylation of methyl iodide, is at least partially aqueous.
• To a decreasing extent, acetic anhydride is also prepared by the reaction of ketene with acetic acid at 45–55 °C and low pressure (0.05–0.2 bar).
• H2C=C=O + CH3COOH → (CH3CO)2O (ΔH = −63 kJ/mol)
• Ketene is generated by dehydrating acetic acid at 700–750 °C in the presence of triethyl phosphate as a catalyst or by the thermolysis of acetone at 600–700 °C in the presence of carbon disulfide as a catalyst.– CH3COOH H2C=C=O + H2O (ΔH = +147 kJ/mol)– CH3COCH3 → H2C=C=O + CH4
• The route from acetic acid to acetic anhydride via ketene was developed by Wacker Chemie in 1922.
Acetic anhydride reactions• The reaction of acetic anhydride with ethanol yields ethyl
acetate:(CH3CO)2O + CH3CH2OH → CH3CO2CH2CH3 +
CH3COOH• Aromatic rings are acetylated in the presence of an acid
catalyst. Illustrative is the conversion of benzene to acetophenone:– (CH3CO)2O + C6H6 → CH3COC6H5 + CH3CO2H
• Ferrocene may be acetylated too– Cp2Fe + (CH3CO)2O → CpFe(C5H4COCH3)Hydrolysis
(CH3CO)2O + H2O → 2 CH3CO2H
Acetic anhydride Applications• Ac2O is mainly used for acetylations leading to
commercially significant materials. • Its largest application is for the conversion of
cellulose to cellulose acetate, which is a component of photographic film and other coated materials.
• Similarly it is used in the production of aspirin, acetylsalicylic acid, which is prepared by the acetylation of salicylic acid.
• In starch industry, acetic anhydride is a common acetylation compound, used for the production of modified starches
Formaldehyde• Structure
• formol, methyl aldehyde, methylene oxide, methanal
Formaldehyde-Properties
• Molecular Formula• Molar Mass• Appearance• Melting Point• Boiling Point• Molecular shape
• CH2O
• 30.026g/ mol• Colourless lgas• −92.6 °C, • -21°C, • Trigonal planar
Formaldehyde• Formaldehyde is an organic compound
with the formula CH2O.
• As the simplest aldehyde, it is an important precursor to many other chemical compounds, especially for polymers.
• In view of its widespread use, toxicity and volatility, exposure to formaldehyde is a significant consideration for human health.
Formaldehyde-Production• Formaldehyde is produced industrially by the catalytic
oxidation of methanol. The most common catalysts are silver metal or a mixture of an iron and molybdenum or vanadium oxides.
• In the more commonly used FORMOX process methanol and oxygen react at ca. 250–400 °C in presence of iron oxide in combination with molybdenum and/or vanadium to produce formaldehyde according to the chemical equation:– 2 CH3OH + O2 → 2 CH2O + 2 H2O
• The silver-based catalyst usually operates at a higher temperature, about 650 °C. Two chemical reactions on it simultaneously produce formaldehyde: that shown above and the dehydrogenation reaction:– CH3OH → H2CO + H2