Download Quantum Theory Bondi..

Quantum Theory Bonding and Chemical Industries
1. Discuss chemistry of Cholesterol.
Cholesterol's Tail is a Hydrocarbon
Like the steroid ring structure, cholesterol's hydrocarbon tail is made up entirely of
hydrogen and carbon.
The Hydrocarbon Tail is Non-Polar
In the lesson on the hydroxyl group, you learned that the electrons in a bond between
oxygen and hydrogen are more attracted to the oxygen. The electrons behave like a
cloud surrounding the two atoms, but the cloud is more dense towards the oxygen.
Another way of saying this is that there is a significant difference
in electronegativity between hydrogen and oxygen.
The oxygen is more electronegative, pulling the electrons toward itself, so, although
the hydroxyl group as a whole is electrically neutral, the side toward the oxygen has
a slight negative charge and the side toward the hydrogen has a slight positive
charge.
This is not the case in the hydrocarbon tail. The electronegativity of hydrogen and
carbon are very similar, so the electron cloud is distributed evenly over the two
atoms.
Carbon-hydrogen bonds are said to be non-polar because they do not have positive
and negative poles within themselves.
Polar Molecules are Water-Soluble — Non-Polar Molecules
are Fat-Soluble
While polar groups like the hydroxyl group and polar molecules like water can make
relatively strong intermolecular bonds (although these bonds are much weak than
the covalent intramolecular bonds) with each other because of the attraction
between the partial positive and negative charges, non-polar groups and non-polar
molecules form very weak attractions between each other.
For this reason, polar molecules dissolve in other polar molecules, and non-polar
molecules dissolve in other non-polar molecules. This results in a division between
water-soluble molecules (polar), and fat-soluble molecules (non-polar).
The Process of Dissolving
This might not be immediately obvious. Consider what it takes for something to
dissolve in water:
Water molecules form large clusters. Most things that will dissolve in water are
clustered together in the form of a crystal — salt, for example. In order for salt to
dissolve in water, three things must happen:



The bonds between the sodium and chloride ions must be broken
The bonds holding the clusters of water molecules must be broken
Bonds must be formed between water molecules and the sodium and
chloride ions, so that each ion is enveloped in its own "cage" of water
molecules.
Remember that the attractive forces between polar molecules are strong, and that
the attractive forces between non-polar molecules are weak. In order to break the
strong, polar bonds between water molecules, the molecule or ion that is trying to
dissolve must be either a polar molecule or a charged ion, both of which
have strong attractive forces.
Dissolving oil, on the other hand, into water, will not work because the weak, nonpolar bonds between fat molecules do not possess strong enough attractive forces
to break up the water molecules. This is true even though the forces within the oil
are weak and easy to break apart, because the oil will only break apart if it has
something else to bond to, and water, hiding in its own cluster, is unavailable.
But dissolving two fat-soluble substances together will work, because, even though
neither substance exerts a particular strong force in breaking apart the other, the
forces holding each together are so weak that they break apart readily.
Cholesterol is Amphipathic
Since cholesterol contains a polar hydroxyl group, on the one hand, and a non-polar
steroid ring structure and hydrocarbon tail, on the other, it has both a water-soluble
region and a fat-soluble region.
Molecules that have both water-soluble and fat-solbule properties are
called amphipathic. Cholesterol's properties as an amphipathic molecule are
important to its function in the human body.
Although cholesterol contains a water-soluble portion, however, it still is not watersoluble enough to dissolve in the blood. It must therefore be transported in
lipoproteins. To learn about lipoproteins, continue on to the next lesson.
2.
Write a note on medicinal importance of peptides.
Peptides (from the Greek πεπτός, "digested" from πέσσειν "to digest") are
short polymers of amino acid monomers linked by peptide bonds. They are distinguished
from proteins on the basis of size, typically containing less than 50 monomer units. The shortest
peptides aredipeptides, consisting of two amino acids joined by a single peptide bond. There are
also tripeptides, tetrapeptides, etc. Amino acids which have been incorporated into a peptide are
termed "residues"; every peptide has a N-terminus and C-terminus residue on the ends of the
peptide (except for cyclic peptides). A polypeptide is a long, continuous, and unbranched
peptide. Proteins consist of one or more polypeptides arranged in a biologically functional way
and are often bound to cofactors, or other proteins.
The size boundaries which distinguish peptides, polypeptides, and proteins are arbitrary. Long
peptides such as amyloid beta can be considered proteins, whereas small proteins such
as insulin can be considered peptides.
Milk peptides
Milk peptides are formed from milk proteins by enzymatic breakdown by digestive
enzymes or by the proteinases formed by lactobacilli during the fermentation of milk.
Several milk peptides have been shown to have antihypertensive effects in animal and in
clinical studies (see also Lactotripeptides).
Ribosomal peptides
Ribosomal peptides are synthesized by translation of mRNA. They are often subjected
to proteolysis to generate the mature form. These function, typically in higher organisms,
as hormones and signaling molecules. Some organisms produce peptides as antibiotics,
such as microcins.[1] Since they are translated, the amino acid residues involved are
restricted to those utilized by the ribosome. However, these peptides frequently
have posttranslational modifications, such as phosphorylation, hydroxylation, sulfonation,
palmitylation, glycosylation and disulfide formation. In general, they are linear,
although lariat structures have been observed.[2] More exotic manipulations do occur,
such as racemization of L-amino acids to D-amino acids in platypus venom.[3]
Nonribosomal peptides
These peptides are assembled by enzymes that are specific to each peptide, rather than
by the ribosome. The most common non-ribosomal peptide is glutathione, which is a
component of theantioxidant defenses of most aerobic organisms.[4] Other nonribosomal
peptides are most common in unicellular organisms, plants, and fungi and are
synthesized by modular enzyme complexes called nonribosomal peptide
synthetases.[5] These complexes are often laid out in a similar fashion, and they can
contain many different modules to perform a diverse set of chemical manipulations on the
developing product.[6] These peptides are often cyclic and can have highly-complex cyclic
structures, although linear nonribosomal peptides are also common. Since the system is
closely related to the machinery for building fatty acids and polyketides, hybrid
compounds are often found. The presence of oxazoles or thiazoles often indicates that
the compound was synthesized in this fashion.[7]
3.
Write general method for synthesis of flavones, isoflavones and flavonoids.
Methods in Organic Synthesis
Methods in Organic Synthesis (MOS) is an alerting service covering the most important current
developments in organic synthesis. It is designed with the synthetic organic chemist in mind, providing
informative reaction schemes and covering new reactions and new methods.
The information is available in a printed publication containing around 200 new reaction schemes each
month, as a text-searchable web database, and as a structure searchable database (via Accelrys Ltd).
The service covers such topics as:

New reactions and reagents

Functional group changes

The introduction of chiral centres

Enzyme and biological transformations
Items are selected for inclusion in MOS only where there is detail of novel or interesting features in organic
synthetic methods, so that there are no routine preparations to plough through.
Each MOS item includes reaction schemes, title and bibliographic details, and the items are categorised by
five indexes: Author, Product, Reaction, Reactant and Reagent.
Browse the Online Database
Subscribers to the monthly, printed bulletin also have free access to MOS Online - the text searchable web
database which allows users to search across items published in MOS from January 2000 to date.
An email alerting service is available, allowing users to sign up for an email message every time the
contents of a new monthly bulletin are published online.
4.
Explain Hantzsch pyridine synthesis with mechanism.
Hantzsch pyridine synthesis
From Wikipedia, the free encyclopedia
The Hantzsch pyridine synthesis or Hantzsch dihydropyridine synthesis is a multicomponent organic reaction between an aldehyde such as formaldehyde, 2
equivalents of a β-keto ester such asethyl acetoacetate and a nitrogen donor such
as ammonium acetate or ammonia.[1] The initial reaction product is a
dihydropyridine which can be oxidized in a subsequent step to a pyridine. The
driving force for this second reaction step is aromatization. This reaction was
reported in 1881 by Arthur Rudolf Hantzsch.
A 1,4-dihydropyridine dicarboxylate is also called a 1,4-DHP compound or
a Hantzsch compound. These compounds are an important class of calcium channel
blockers and as such commercialized in for
instance nifedipine, amlodipine or nimodipine.
The reaction has been demonstrated to proceed in water as reaction solvent and
with direct aromatization by ferric chloride or potassium permanganate in a one-pot
synthesis.[2]
The Hantzsch dihydropyridine synthesis is found to benefit from microwave
chemistry.[
5.
Write short note on Lignin and Pectines.
Lignin or lignen is a complex chemical compound most commonly derived from wood, and an
integral part of the secondary cell walls ofplants[1] and some algae.[2] The term was introduced in
1819 by de Candolle and is derived from the Latin word lignum,[3] meaning wood. It is one of the
most abundant organic polymers on Earth, exceeded only by cellulose, employing 30% of nonfossil organic carbon,[4]and constituting from a quarter to a third of the dry mass of wood. As
a biopolymer, lignin is unusual because of its heterogeneity and lack of a defined primary
structure. Its most commonly noted function is the support through strengthening of wood
(xylem cells) in trees.[5][6][7]
Global production of lignin is around 1.1 million tonnes per year and is used in a wide range of
low volume, niche applications where the form but not the quality is important. [8]
Lignin fills the spaces in the cell wall between cellulose, hemicellulose, and pectin components,
especially in tracheid, sclereid andxylem cells. It is covalently linked to hemicellulose and,
therefore, crosslinks different plant polysaccharides, conferring mechanical strength to the cell
wall and by extension the plant as a whole.[9] It is particularly abundant in compression wood but
scarce in tension wood.
Lignin plays a crucial part in conducting water in plant stems. The polysaccharide components of
plant cell walls are highly hydrophilicand thus permeable to water, whereas lignin is
more hydrophobic. The crosslinking of polysaccharides by lignin is an obstacle for water
absorption to the cell wall. Thus, lignin makes it possible for the plant's vascular tissue to conduct
water efficiently.[10] Lignin is present in all vascular plants, but not in bryophytes, supporting the
idea that the original function of lignin was restricted to water transport. However, it is present
in red algae, which seems to suggest that the common ancestor of plants and red algae also
synthesised lignin. This would suggest that its original function was structural; it plays this role in
the red alga Calliarthron, where it supports joints between calcified segments.[2]
6.
What are purines? Prove the structure of uric acid.
A purine is a heterocyclic aromatic organic compound, consisting of a pyrimidine ring fused to
an imidazole ring. Purines, including substituted purines and their tautomers, are the most widely
distributed kind of nitrogen-containing heterocycle in nature.[1]
Purines and pyrimidines make up the two groups of nitrogenous bases, including the two groups
of nucleotide bases. Two of the fourdeoxyribonucleotides and two of the four ribonucleotides, the
respective building-blocks of DNA and RNA, are purines.
The quantity of naturally occurring purines produced on earth is huge. Two of the four bases
in nucleic acids, adenine (2) and guanine (3), are purines. In DNA, these bases form hydrogen
bonds with their complementary pyrimidines thymine and cytosine, respectively. This is called
complementary base pairing. In RNA, the complement of adenine is uracil instead of thymine.
Other notable purines are hypoxanthine (4), xanthine (5), theobromine (6), caffeine (7), uric
acid (8) and isoguanine (9).
[edit]Functions
Aside from the crucial role of purines (adenine and guanine) in DNA and RNA, purines are also
significant components in a number of other important biomolecules, such as ATP, GTP, cyclic
AMP,NADH, and coenzyme A. Purine (1) itself, has not been found in nature, but it can be
produced by organic synthesis.
They may also function directly as neurotransmitters, acting upon purinergic receptors.
Adenosine activates adenosine receptors.
7.
Discuss the attachment of sugar and phosphate in nucleotide.
8.
Write a note on angiotensin.