BASE OF ORGANIC CHEMISTRY – KIRTI NIRALWAD

BASE OF ORGANIC CHEMISTRY –				plastics, food, explosives, drugs, petrochemicals,
Brief History:-				to name but a few) and (apart from a very few
Jöns Jacob Berzelius, a physician by				exceptions) they form the basis of all earthly life
trade, first coined the term "organic chemistry" in				processes.
1807 for the study of compounds derived from				Organic chemistry, like all areas of science,
biological sources. Up through the early 19th				evolves with particular waves of innovation. These
century, naturalists and scientists observed critical				innovations are motivated by practical
differences between compounds that were				considerations as well as theoretical innovations.
derived from living things and those that were				The area is however underpinned financially by
not.				the very large applications in polymer science,
Chemists of the period noted that there				pharmaceutical chemistry, and agrichemicals.
seemed to be an essential yet inexplicable
difference between the properties of the two				Properties :-
different types of compounds. The vital force				Physical properties of organic compounds typically
theory (sometimes called "vitalism") was				of interest include both quantitative and qualitative
therefore proposed (and widely accepted) as a				features. Quantitative information include melting
way to explain these differences. Vitalism				point, boiling point, and index of refraction.
proposed that there was something called a "vital				Qualitative properties include odor, solubility, and
force" which existed within organic material but did				color.
not exist in any inorganic materials.				Melting and boiling properties
				In contrast to many inorganic materials, typical
				organic compounds typically melt and boil. In earlier
� Synthesis of Urea				times, the melting point (m.p.) and boiling point
				(b.p.) provided crucial information on the purity and
�				identity of organic compounds. The melting and
				boiling points correlate with the polarity of the
				molecules and their molecular weight. Some
				organic compounds, especially symmetrical ones,
Friedrich Wöhler is widely regarded				sublime, that is they evaporate without melting. A
as a pioneer in organic chemistry as a result of his				well known example of a sublimable organic
synthesizing of the biological compound urea (a				compound is para-dichlorobenzene, the odiferous
component of urine in many animals) utilizing what				constituent of mothballs. Organic compounds are
is now called "the Wöhler synthesis."				usually not very stable at temperatures above
Wöhler mixed silver or lead cyanate with				300 °C, although some exceptions exist. Color
ammonium nitrate; this was supposed to yield				Organic compounds are typically colorless or white.
ammonium cyanate as a result of an exchange				The situation is quite different for organic
reaction, according to Berzelius's dualism theory.				compounds that contain several adjacent multiple
Wöhler, however, discovered that the end				bonds. These compounds, where the double
product of this reaction is not ammonium cyanate				bonds are "conjugated" can be deeply colored.
(NH4OCN), an inorganic salt, but urea ((NH2)2CO),				The biological pigments carotene and heme
a biological compound. (Furthermore, heating				illustrate the relationship between "conjugation"
ammonium cyanate turns it into urea.) Faced with				and color. Impure organic compounds, as well as
this result, Berzelius had to concede that				many biological materials, often are yellow or
(NH2)2CO and NH4OCN were isomers. Until this				brownish owing to the presence of trace amounts
discovery in the year 1828, it was widely believed				of intensely colored impurities. Solubility
by chemists that organic substances could only be				Neutral organic compounds tend to be
formed under the influence of the "vital force" in				hydrophobic, that is they are less soluble in water
the bodies of animals and plants. Wöhler's				than in organic solvents. Exceptions include organic
synthesis dramatically proved that view to be				compounds that contain ionizable groups as well as
false.				low molecular weight alcohols, amines, and
Urea synthesis was a critical discovery for				carboxylic acids where hydrogen bonding occurs.
biochemists because it showed that a compound				Organic compounds tend to dissolve in organic
known to be produced in nature only by biological				solvents. Solvents can be either pure substances
organisms could be produced in a laboratory under				like ether or ethyl alcohol, or mixtures, such as
controlled conditions from inanimate matter. This				the paraffinic solvents such as the various
"in vitro" synthesis of organic matter disproved				petroleum ethers and white spirits, or the range
the common theory (vitalism) about the vis vitalis,				of pure or mixed aromatic solvents obtained from
a transcendent "life force" needed for producing				petroleum or tar fractions by physical separation
organic compounds.				or by chemical conversion. Solubility in the
				different solvents depends upon the solvent type
Organic vs Inorganic Chemistry:-				and on the functional groups if present. Solid
Although originally defined as the chemistry of				state properties
biological molecules, organic chemistry has since				Various specialized properties are of interest
been redefined to refer specifically to carbon				depending on applications, e.g. thermo-mechanical
compounds — even those with non-biological				and electro-mechanical such as piezoelectricity,
origin. Some carbon molecules are not considered				electrical conductivity (see organic metals), and
organic, with carbon dioxide being the most well				electro-optical (e.g. non-linear optics) properties. For
known and most common inorganic carbon				historical reasons, such properties are mainly the
compound, but such molecules are the exception				subjects of the areas of polymer science and
and not the rule.				materials science.
Organic chemistry focuses on carbon and				Toxicity
following movement of the electrons in carbon				Living matter including food, drugs are collections
chains and rings, and also how electrons are				organic compounds, so the potential beneficial and
shared with other carbon atoms and				harmful aspects of organic compounds span the
heteroatoms. Organic chemistry is primarily				entire range required for life to some of the most
concerned with the properties of covalent bonds				dangerous materials known. Indicative of the
and non-metallic elements, though ions and metals				power of organic chemistry, the biomolecule called
do play critical roles in some reactions.				botulism toxin ("Botox") is lethal at the level of
The applications of organic chemistry are myriad,				less than a microgram.
and include all sorts of plastics, dyes, flavorings,
scents, detergents, explosives, fuels and many,				Nomenclature?:-
many other products. Read the ingredient list for				The names of organic compounds are either
almost any kind of food that you eat — or				systematic, following logically from a set of rules,
even your shampoo bottle — and you will see				or nonsystematic, following various traditions.
the handiwork of organic chemists listed there.				Systematic nomenclature is stipulated by
				recommendations from IUPAC. Systematic
Major Advances in the Field of Organic				nomenclature starts with the name for a parent
Chemistry:-				structure within the molecule of interest. This
Of course no description of a text should be				parent name is then modified by prefixes,
without at least a mention of Antoine Laurent				suffixes, and numbers to unambiguously convey
Lavoisier. The French chemist is often called the				the structure. Given that millions of organic
"Father of Modern Chemistry" and his place is first				compounds are known, rigorous use of
in any pantheon of great chemistry figures. Your				systematic names can be cumbersome. Thus,
general chemistry textbook should contain				IUPAC recommendations are more closely
information on the specific work and discoveries				followed for simple compounds, but not complex
of Lavoisier — they will not be repeated here				molecules. To use the systematic naming, one
because his discoveries did not relate directly to				must know the structures and names of the
organic chemistry in particular.				parent structures. Parent structures include
Berzelius and Wöhler are discussed above, and				unsubstituted hydrocarbons, heterocycles, and
their work was foundational to the specific field of				monofunctionalized derivatives thereof.
organic chemistry. After those two, three more				Nonsystematic nomenclature is simpler and
scientists are famed for independently proposing				unambiguous, at least to organic chemists.
the elements of structural theory. Those chemists				Nonsystematic names do not indicate the
were August Kekulé, Archibald Couper and				structure of the compound. Nonsystematic names
Alexander Butlerov.				are common for complex molecules, which
Kekulé was a German, an architect by training,				includes most natural products. Thus, the
and he was perhaps the first to propose that the				informally named lysergic acid diethylamide is
concept of isomerism was due to carbon's				systematically named (6aR, 9R)-N,
proclivity towards forming four bonds. Its ability to				N-diethyl-7-methyl-4, 6, 6a, 7, 8,
bond with up to four other atoms made it ideal				9-hexahydroindolo-[4, 3-fg]
for forming long chains of atoms in a single				quinoline-9-carboxamide.
molecule, and also made it possible for the same				With the increased use of computing, other
number of atoms to be connected in an				naming methods have evolved that are intended
enormous variety of ways. Couper, a Scot, and				to be interpreted by machines. Two popular
Butlerov, a Russian, came to many of the same				formats are SMILES and InChI.
conclusions at the same time or just a short time				Structural drawings
after.				Organic molecules are described more commonly
Through the nineteenth century and into the				by drawings or structural formulas, combinations
twentieth, experimental results brought to light				of drawings and chemical symbols. The line-angle
much new knowledge about atoms, molecules and				formula is simple and unambiguous. In this system,
molecular bonding. In 1916 it was Gilbert Lewis of				the endpoints and intersections of each line
U.C. Berkeley who described covalent bonding				represent one carbon, and hydrogen atoms can
largely as we know it today (electron-sharing).				either be notated explicitly or assumed to be
Nobel laureate Linus Pauling further developed				present as implied by tetravalent carbon. The
Lewis' concepts by proposing resonance while he				depiction of organic compounds with drawings is
was at the California Institute of Technology. At				greatly simplified by the fact that carbon in almost
about the same time, Sir Robert Robinson of				all organic compounds has four bonds, oxygen
Oxford University focused primarily on the				two, hydrogen one, and nitrogen three.
electrons of atoms as the engines of molecular
change. Sir Christopher Ingold of University				Arrhenius Definition: Hydroxide and Hydronium
College, London, organized what was known of				Ions:-
organic chemical reactions by arranging them in				The first and earliest definition of acids and bases
schemes we now know of as mechanisms, in				was proposed in the 1800's by Swedish scientist
order to better understand the sequence of				Svante Arrhenius, who said that an acid was
changes in a synthesis or reaction.				anything that dissolved in water to yield H+ ions
The field of organic chemistry is probably the				(like stomach acid HCl, hydrochloric acid), and a
most active and important field of chemistry at				base was anything that dissolved in water to give
the moment, due to its extreme applicability to				up OH- ions (like soda lye NaOH, sodium
both biochemistry (especially in the pharmaceutical				hydroxide). Acids and bases were already widely
industry) and petrochemistry (especially in the				used in various occupations and activities of the
energy industry). Organic chemistry has a				time, so Arrhenius' definition merely attempted to
relatively recent history, but it will have an				explained well-known and long-observed
enormously important future, affecting the lives				phenomenon.
of everyone around the world for many, many				Although simple, at the time this definition of the
years to come. Organic chemistry :-				two types of substances was significant. It
Organic chemistry is a discipline within chemistry				allowed chemists to explain certain reactions as
which involves the scientific study of the				ion chemistry, and it also expanded the ability of
structure, properties, composition, reactions, and				scientists of the time to predict certain chemical
preparation (by synthesis or by other means) of				reactions. The definition left a great deal wanting,
hydrocarbons and their derivatives. These				however, in that many types of reactions that did
compounds may contain any number of other				not involve hydroxide or hydronium ions directly
elements, including hydrogen, nitrogen, oxygen,				remained unexplained.
the halogens as well as phosphorus, silicon and				Many general chemistry classes (especially in the
sulfur.[1][2][3].				lower grades or introductory levels) still use this
Because of their unique properties, multi-carbon				simple definition of acids and bases today, but
compounds exhibit extremely large variety and				modern organic chemists make further distinctions
the range of application of organic compounds is				between acids and bases than the distinctions
enormous. They form the basis of, or are				provided under Arrhenius's definition.
important constituents of many products (paints,

Rpma

BASE OF ORGANIC CHEMISTRY – KIRTI NIRALWAD