Answers to Concept Checks

2.1

Structural  isomers share   a   molecular   formula,    and not necessarily anything    else.

Cyclopropanol,  acetone,    and prop-2-ene-1-ol are all structural  isomers of  each    other   with    the

chemical    formula C 3 H 6 O.  2-propanol  has the chemical    formula C 3 H 8 O.

Physical    properties  are aspects of  a   compound    that    do  not play    a   role    in  changing    chemical

composition.    Examples    include melting point,  boiling point,  solubility, odor,   color,  and density.

Chemical    properties  are aspects of  a   compound    that    change  chemical    composition;    in  organic

chemistry,  chemical    properties  are usually dictated    by  the reactivity  of  various functional  groups.

2.2
Conformational isomers are stereoisomers with the same molecular connectivity at different
points of rotation around a single bond. Configurational isomers are stereoisomers with differing
molecular connectivity.

Definition Same Physical

Properties?

Same    Chemical

Properties?

Enantiomers Nonsuperimposable   mirror  images  (differ at  all

chiral  carbons,    with    no  plane   of  symmetry)

Yes,    except: rotation    of

plane-polarized light

Yes,    except: reactions   in

chiral  environments

Diastereomers Non-mirror-image  optical isomers (differ by  at

least   one,    but not all chiral  carbons)

No No   (although   may be

similar)

A   meso    compound    contains    chiral  centers but also    has an  internal    plane   of  symmetry.   This

means   that    the molecule    is  overall achiral and will    not rotate  plane-polarized light.

2.3
(E) and (Z) configurations refer to arrangement of groups around a double bond. (Z) describes
when the two highest-priority groups are on the same side; (E) describes when the two highest-
priority groups are on opposite sides.