(a) What are the C— C— C bond angles in diamond?(b) What are they in graphite (in one sheet)? (c) Whatatomic orbitals are involved in the stacking of graphitesheets with each other? The solid wedges in the figure indicate bonds from carbonthat come out of the plane of the page; the dashed wedgesindicate bonds that lie behind the plane of the page.(a) What is the hybridization of orbitals at each carbonatom? What angles do you expect between the bonds?(b) Now imagine that the polymer is polypropylenerather than polyethylene. Draw structures for polypropylenein which (i) the CH3 groups all lie on thesame side of the plane of the paper (this form is calledisotactic polypropylene), (ii) the CH3 groups lie on alternatingsides of the plane (syndiotactic polypropylene),or (iii) the CH3 groups are randomly distributedon either side (atactic polypropylene). Which of theseforms would you expect to have the highest crystallinityand melting point, and which the lowest? Explainin terms of intermolecular interactions and molecularshapes.(c) Polypropylene fibers have been employed in athleticwear. The product is said to be superior to cotton orpolyester clothing in wicking moisture away from thebody through the fabric to the outside. Explain thedifference between polypropylene and polyester or cotton(which has many ¬OH groups along the molecularchain) in terms of intermolecular interactions withwater.
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.
(a) What are the C— C— C bond angles in diamond?
(b) What are they in graphite (in one sheet)? (c) What
atomic orbitals are involved in the stacking of graphite
sheets with each other?
The solid wedges in the figure indicate bonds from carbon
that come out of the plane of the page; the dashed wedges
indicate bonds that lie behind the plane of the page.
(a) What is the hybridization of orbitals at each carbon
atom? What angles do you expect between the bonds?
(b) Now imagine that the
rather than polyethylene. Draw structures for polypropylene
in which (i) the CH3 groups all lie on the
same side of the plane of the paper (this form is called
isotactic polypropylene), (ii) the CH3 groups lie on alternating
sides of the plane (syndiotactic polypropylene),
or (iii) the CH3 groups are randomly distributed
on either side (atactic polypropylene). Which of these
forms would you expect to have the highest crystallinity
and melting point, and which the lowest? Explain
in terms of intermolecular interactions and molecular
shapes.
(c) Polypropylene fibers have been employed in athletic
wear. The product is said to be superior to cotton or
polyester clothing in wicking moisture away from the
body through the fabric to the outside. Explain the
difference between polypropylene and polyester or cotton
(which has many ¬OH groups along the molecular
chain) in terms of intermolecular interactions with
water.
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