Molecular Shape and Bonding

Question 1

What do functional groups determine in drugs? (6)

Answer 1

• bioavailability
• GIT absorption
• first pass metabolism
• binding to receptor
• route of admin
• time course of effect

Question 2

What is HMG-CoA reductase?

Answer 2

• rate determining enzyme
• located in hepatic tissue
• produces mevalonate
• atorvastatin is a competitive inhibitor of this

Question 3

does electronegativity increase from left to right or right to left?

Answer 3

left to right

Question 4

why does electronegativity decrease as you go down the group?

Answer 4

because there is an increased distance between valance electrons and nucleus

Question 5

what is ground-state electron configuration?

Answer 5

most stable, lowest energy electron configurations an atom

Question 6

Chemical bonding theory: why do atoms bond?

Answer 6

because the compound that results is more stable and lower in energy than the separate atoms

Question 7

why is there 8 electrons in valence shell?

Answer 7

to impart special stability to noble gas elements in 8A

Question 8

what is a polar covalent bond?

Answer 8

a covalent bond in which the electron distribution between atoms is unsymmetrical due to a difference in electronegativity

Question 8

what is a polar covalent bond?

Answer 8

a covalent bond in which the electron distribution between atoms is unsymmetrical due to a difference in electronegativity

Question 9

when are ionic bonds formed?

Answer 9

when the difference in electronegativity between the two atoms is greater than 1.7

Question 10

when are covalent bonds formed?

Answer 10

when the different in electronegativity between the two atoms is less than 1.7

Question 11

when are polar/non-polar covalent bonds formed?

Answer 11

non polar- <0.4

polar- 0.4-1.7

Question 12

what is the inductive effect? and what type of atoms have it?

Answer 12

• an atoms ability to polarise a bond
• electron-withdrawing effect transmitted through o bonds
• electronegative elements have an electron-withdrawing inductive effect

Question 13

what is a dipole moment?

Answer 13

a measure of the net polarity of a molecule

Question 14

how does molecular polarity occur?

Answer 14

results from the vector summation (geometry) of all individual bond polarities and lone pair contributions in the molecule

Question 15

what is the equation for formal charge?

Answer 15

formal charge=number of valence electrons-(number of lone pair electrons+1/2 number of bonding electrons)

Question 16

what is a free radical?

Answer 16

species where one atom has a single unpaired electron

Question 17

what is valence bond theory?

Answer 17

bonding theory that describes a covalent bond resulting from the overlap of two atomic orbitals.

Question 18

in what other ways can carbon hybridise? (5)

Answer 18

• two p orbitals can combine with the s orbital to give three sp2 orbitals.
• one unhybridised p orbital remains
• electron repulsion minimised by three sp2 orbital lying in a plane
• bond angles all close to 120-trigonal planar
• unhybridised p orbital is perpendicular to the plane