The two strands of the DNA molecule are held together by hydrogen bonds between base pairs.When an enzyme unzips the molecule to separate the two strands, it has to break these hydrogen bonds. A simplified model represents a hydrogen bond as the electrostatic interaction of four point charges arranged along a straight line. The figure shows the arrangement of charges for one of the hydrogen bonds between adenine and thymine. Estimate the energy that must be supplied to break this bond. Hydrogen bond 92 93 WIŲ 0.180 nm N 91 0.120 nm Adenine H 0.120 nm Thymine C 94 where 9₁ = -0.490e, q2 = +0.490e, 93 = -0.590e, and 94 = +0.590e. The energy that must be supplied to break the hydrogen bond is J.
Formal Charges
Formal charges have an important role in organic chemistry since this concept helps us to know whether an atom in a molecule is neutral/bears a positive or negative charge. Even if some molecules are neutral, the atoms within that molecule need not be neutral atoms.
Polarity Of Water
In simple chemical terms, polarity refers to the separation of charges in a chemical species leading into formation of two polar ends which are positively charged end and negatively charged end. Polarity in any molecule occurs due to the differences in the electronegativities of the bonded atoms. Water, as we all know has two hydrogen atoms bonded to an oxygen atom. As oxygen is more electronegative than hydrogen thus, there exists polarity in the bonds which is why water is known as a polar solvent.
Valence Bond Theory Vbt
Valence bond theory (VBT) in simple terms explains how individual atomic orbitals with an unpaired electron each, come close to each other and overlap to form a molecular orbital giving a covalent bond. It gives a quantum mechanical approach to the formation of covalent bonds with the help of wavefunctions using attractive and repulsive energies when two atoms are brought from infinity to their internuclear distance.
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