C7. Stereochemistry

Question 1

sp3 hybridized carbon is what shape?

Answer 1

tetrahedral (one note for structure) 109.5

Question 2

sp2 hybridized carbon is what shape?

Answer 2

trigonal (one note) 120

Question 3

sp hybrized carbon is what shape?

Answer 3

linear (one note) 180

Question 4

what are structural or constitutional isomers?

Answer 4

compounds with same molecular formula, but different arrangement of
atoms

Question 5

what are stereoisomers?

Answer 5

compounds that are exactly the same (same molecular formula and same sequence of covalently bonded atoms), but differ in the way the various groups are orientated in space

Question 6

what are conformational stereoisomers?

Answer 6

-Different conformations of the same molecule
– Interconvert easily through rotation around single bond, ring
flip
– E.g. ethane (one note)

Question 7

what is configurational isomerism?

Answer 7

– Identical groups differ in how they are arranged around the
same central C-atom
– Do not easily interconvert
– Need to break a bond to interconvert
– Thalidomide is an example of a configurational stereoisomer

Question 8

what is newman projection

Answer 8

view of a molecules from end (staggered conformer and eclipsed conformer)

Question 9

what is gauche?

Answer 9

The relationship between two atoms or groups whose dihedral angle is more than 0 (i.e., eclipsed) but less than 120 (i.e., the next eclipsed conformation). It is 60 degrees- when large species are behind each other, most repulsion so highest energy.

Question 10

what is anti?

Answer 10

when large atoms are opposite each other (180 degrees) - lowest energy conformation as least repulsion

Question 11

Describe butane conformations

Answer 11

one note for sructure

Question 12

what is the predominant form of cyclohexane?

Answer 12

chair conformation, there is no eclipsing in chair conformation. hydrogens are axial (three going up, three going down) or hydrogens are equatorial (going to the side)- ONE NOTE

Question 13

Describe the two conformation of cyclohexane

Answer 13

interconversion of conformers via ring flip
changes axial / equatorial relationship;
conformers have same energy- ONE NOTE

Question 14

Describe cyclohexane boat strcture

Answer 14

-no ring strain
-eclipsing in boat conformation
-flag-pole interaction in boat
-eclipsing and flag-pole
-interaction reduced in twist-boat
-both higher energy than chair
ONE NOTE FOR STRUCTURE