Organic Chemistry -1 Flashcards
what lead to the synthesis of the organic cpds in the laboratory
Berzilius, a Swedish chemist
proposed that a ‘vital force’ was responsible for the
formation of organic compounds. However, this notion
was rejected in 1828 when F. Wohler synthesised an
organic compound, urea from an inorganic compound,
ammonium cyanate.
NH4CNO —-heat—-> NH2CONH2
The pioneering synthesis of acetic acid by Kolbe (1845)
and that of methane by Berthelot (1856) showed
conclusively that organic compounds could be synthesised
from inorganic sources in a laboratory.
why is the carbon atom always tetravlent
because it is eneergetically difficult for carbon to gain or lose 4 e-s to attain stable noble gas configuration.
therefore it prefers to share e-s
how does bond length depend upon hybridisation
as p orbital is larger than s orbital as we move from sp3 to sp2 to sp, the p charac descreases form 75% t 66.6% to 50%
and bond length also decreases from sp3>sp2>sp
bond length directly prop to p charact
bond length inversely prop to s charac
bond strength directly prop to s charac
how does electronegativity depend upon hybridisation
s orbital has more electronegatiev characater
electronegativity dirreclty prop to s charact
sp>sp2>sp3
what is the 3 dimensional representation of molecules
For
example, by using solid ( ) and dashed
( ) wedge formula, the 3-D image of a
molecule from a two-dimensional picture
can be perceived. In these formulas the
solid-wedge is used to indicate a bond
projecting out of the plane of paper, towards
the observer. The dashed-wedge is used to
depict the bond projecting out of the plane of
the paper and away from the observer. Wedges
are shown in such a way that the broad end
of the wedge is towards the observer. The
bonds lying in plane of the paper are depicted
by using a normal line (—)
classification of organic moecules
(i) Aliphatic/ Open chain molecules/ Acyclic
These compounds are also called as aliphatic
compounds and consist of straight or
branched chain compounds
(ii) Cyclic/Close chain/ ring compounds
(a) homocyclic/carbocyclic- have only c atoms
1. aliphatic cyclic / alycyclic/
Alicyclic (aliphatic cyclic) compounds contain carbon atoms
joined in the form of a ring(cyclohexane, ).
2.Aromatic compounds are special types of
compounds. These include
benzene and other related ring compounds
(benzenoid) like benzene, aniline, phenol,napthalene . Like alicyclic compounds,
aromatic comounds may also have hetero
atom in the ring. Such compounds are called
hetrocyclic aromatic compounds( furan, thiophene/ pyrrole/ pyridine). Non benzenoids do not have benzene ring in their structure( tropone, tropolone)
b) heterocyclic
have S, O , N
tetrahydrofuran
what is a functional group
atom/ grp of atoms joined in a specific manner which is responsible for the characteristic chemical behaviour/ properties of organic cpds.
what is a homologous series
A group or a series of organic compounds each
containing a characteristic functional group
forms a homologous series and the members
of the series are called homologues. The
members of a homologous series can be
represented by general molecular formula and
the successive members differ from each other
in molecular formula by a –CH2 unit.
They have similar chemical properties, can be prepared by the same general method of preparation.
they show gradation in various physical properties such as density, mpt, bpt. etc
what is isomerism? what are isomers
The phenomenon of existence of two or more
compounds possessing the same molecular
formula but different physical and chemical properties is known as
isomerism. Such compounds are called as
isomers
what are structural isomers
Compounds having the same molecular
formula but different structures (manners in
which atoms are linked) are classified as
structural isomers.
chain isomers
When two or more
compounds have similar molecular formula but different carbon skeletons, these are referred
to as chain isomers and the phenomenon is
termed as chain isomerism.
eg pentane
Position isomerism:
When two or more
compounds differ in the position of
substituent atom or functional group on the
carbon skeleton, they are called position
isomers and this phenomenon is termed as
position isomerism. For example, the
molecular formula C3H8O
Functional group isomerism
Two or
more compounds having the same molecular
formula but different functional groups are
called functional isomers and this
phenomenon is termed as functional group
isomerism.
i) alcohols ethers(ethanol, methoxymethanE)
ii) carboxylic acids, esters( ethanoic acid, methyl methanoate)
iii) aldehyde, ketone, unsaturated alcohols, unsaturated esters(propanone, propanal)
iv)aromatic alcohols, ethers and phenols( benzyl alcohol, anisole, 3 cresols)
v) nitroalkanes, nitrites, amino acids
vi) 1, 2 and 3* amines
vii) cyanide, isocyanide
metamerism
It arises due to different alkyl
chains on either side of the divalent functional group
in the molecule. eg: ketones, ethers,
what are stereoisomerS?
The compounds that have the same
constitution and sequence of covalent bonds
but differ in relative positions of their atoms
or groups in space are called stereoisomers.
