Steroisomers

Question Are your right and left socks identical? Are your right and left gloves identical? Your socks are achiral Your gloves are chiral

Chiral vs Achiral Chiral – An object that is nonsuperimposable on its mirror image Your hand Achiral – An object that is superimposable on its mirror image A blank piece of paper

Chiral or Achiral Golf Club –Chiral Teacup –Achiral Corkscrew –Achiral Tennis Racket –Chiral Shoe –Chiral Portrait –Chiral Pencil –Achiral Cube –Achiral

Construct This Molecule

Construct Its Mirror Image Place the Green atom away from the mirror.

Compare the Molecules The molecules you constructed the same? They are chiral molecules They cannot be superimposed on each other They are stereoisomers (enantomers) How do you know?

Comparison of Chiral and Achiral Molecules that do not have a plane of symmetry are chiral If there is a Carbon with 4 different groups there will not be a plane of symmetry A Carbon with different groups is called a stereogenic center

Find the stereogenic center(s) in 3-methylhexane

Draw the two enantomers of 3-methylhexane

Find the stereogenic center(s) in 2,3-dibromobutane

Find the stereogenic center(s) in 1-bromopropane

Differentiating Enantomers Enantomers are differentiated using the R-S or Cahn-Ingold-Prelog (CIP) Convention It is a way to determine the orientation of groups around a stereogenic center Determined by priority of the groups –We have rules for that

Group Priority Rules #1 – Atom with the highest atomic number has the first priority – F>O>N>H #2 – If there are groups with the same atoms continue until they vary (Methyl and Ethyl for example) –Ethyl has priority over methyl

R and S A molecule is R if the 3 highest priority atoms go clockwise A molecule is S if the 3 highest priority atoms go counterclockwise

Grab this molecule!

R or S We are going to assign the molecule an R or S designation. We will use alphabetic color as priority. Meaning green is first Place the White atom away from you. It is the lowest not considered Go in order of priority –Clockwise is R –Counterclockwise is S

Assign the configuration to the following molecule. Then name the molecule

Draw the structure of (R)-2-bromobutane

Do the following 5.33 a and b 5.34 a and b

Aromatic Compounds Contain a benzene ring (C 6 H 6 ) Alternating double bonds (Conjugated) Shown two different ways Kekule Structure or Delocalized Structure

Properties Nonpolar Hybridization? –sp 2 Bond Angles? –120 Cloud of pi bond above and below the ring

Nomenclature When a benzene group is attached as a substituent it loses a H and becomes a phenyl group There are some benzene compounds with common names You should be familiar but do not have to memorize them

Examples Aniline Toluene –Methylbenzene Phenol Styrene

Monosubstituted Aromatics Compounds without common names are named as derivatives of benzene Do not need to give a number because there is only one position

Name the compound

Draw the structure for ethylbenzene

Disubstituted Aromatics When there are two substitutents on an aromatic ring there are two ways to name it. First is by Ortho, Para, Meta Second is by IUPAC

Ortho, Para, Meta These are positions on the benzene ring relative to position 1 Othro represents the 2 and 6 positions Meta represents the 3 and 5 positions Para represents the 4 position Named according the positions of the groups

Ortho, Meta, Para

Name the compound

Draw the structure for o-bromochlorobenzene

Trisubstituted Aromatics Just use numbers for naming and positions Draw the structure for 2,4,6-trimethylphenol