2D structure drawing hem 314 Beauchamp Mechanical Approach to Drawing 2D, 3D and esonance tructures from a condensed line formula. 1. Draw a 2D structure based on given arrangement shown in condensed line formula 2. ount all valence electrons (make up bonds, lone pairs and radical centers) 3. ount electron in sigma bonds generated (connections = skeleton) and compare to total valence electrons 4. If there are excess electrons, add them in as lone pairs to fill valencies of most electronegative atoms first (F>>). 5. If there are still excess electrons place them at alternate carbon positions to spread out electron density and minimize electron/electron repulsion. If there are still excess electrons left add them to carbon atoms with the fewest sigma bonds. 6. If any atoms lack a full octet, look for adjacent lone pair electrons that can be shared. These will make pi bonds. If there is more than one way to do this, there will be structures. Draw as many of these as are obvious. 7. Evaluate formal charge on all of the atoms. 8. Evaluate structures for relative contributions according to the following rules a. More bonds and full octets is most important = best. b. aving charge consistent with relative electronegativities is second best. 9. Write any additional structures using typical patterns of donor and acceptor sites a. alkene, alkyne and pi bonds are connector components and can donate or accept electrons b. donor sites are atoms with lone pairs of electrons (and pi bonds from a ) c. acceptor sites are neutral polar pi bonds and cationic pi bonds (and pi bonds from a ) 10. To decide each atom s 3D shape, hybridization and bond angles a. Use a structure where an atom has its maximum number of bonds (shows necessary 2p orbitals to make any pi bonds (no pi bonds = sp3, one pi bond = sp2, two pi bonds = sp) b. carbocation carbon atoms use an empty 2p orbital in our course. y:\files\classes\314\314 pecial andouts\drawing 2D functional groups home.doc
2D structure drawing hem 314 Beauchamp 1. Donor = lone pair next to empty 2p orbital acceptors (usually on carbon as a carbocation) X X X X sp or sp 2 hybridization is possible on either X or 2 2 2 2 2 2 2 3 2 2 2 2 2 2 F 2 2 2 2 2 F 2 Many other examples are possible. 2 2 2 2. Donor = lone pair next to a pi bond acceptors (polar pi bonds are better acceptors than nonpolar pi bonds) X X X X sp or sp 2 hybridization is possible on either X or 2 2 2 2 2 Interesting Variations 2 3 2 2 2 F 2 3. Donor pi bonds (usually alkene, alkyne or ) next to empty 2p orbital acceptors (usually on carbon as a carbocation) X 3. Donor pi bonds (usually alkene, alkyne or ) next to a polar or cationic pi bond acceptors (polar pi bonds are best =, =, =, =, nitrile, but alkene, alkyne and are possible) alkene or alkene or alkene or alkene or Just a few examples. Many more variations. y:\files\classes\314\314 pecial andouts\drawing 2D functional groups home.doc
2D structure drawing hem 314 Beauchamp 3 2 3 3 2 2 3 2 2 3 2 2 use zig-zag drawing for sp 3 chains 1 o carbocation 1 o carbanion 1 o free radical 3 3 3 3 3 3 2 o carbocation 2 o carbanion 2 o free radical 3 2 3 2 2 3 2 alcohol use zig-zag drawing for sp 3 chains protonated alcohol alkoxide 3 2 3 2 2 3 2 3 2 ether use zig-zag drawing for sp 3 chains protonated ether carbanion free radical y:\files\classes\314\314 pecial andouts\drawing 2D functional groups home.doc
2D structure drawing hem 314 Beauchamp 3 3 3 2 3 3 3 2 o amine use zig-zag drawing for sp 3 chains dialkylammonium ion 2 o amide anion 2 3 2 2 2 2 2 2 monosubstituted alkene 1 o allylic carbocation 1 o allylic carbanion 1 o allylic free radical 3 3 2 2 3 imine 1 o allylic carbanion 1 o allylic free radical y:\files\classes\314\314 pecial andouts\drawing 2D functional groups home.doc
2D structure drawing hem 314 Beauchamp y:\files\classes\314\314 pecial andouts\drawing 2D functional groups home.doc imine 1 o allylic carbanion 3 3 2 2 3 3 2 aldehyde enolate anion protonated carbonyl
2D structure drawing hem 314 Beauchamp 3 3 3 3 3 2 ketone protonated carbonyl enolate anion 3 2 2 2 alkyne propargyl carbocation propargyl carbanion propargyl free radical y:\files\classes\314\314 pecial andouts\drawing 2D functional groups home.doc
2D structure drawing hem 314 Beauchamp 3 3 2 nitrile protonated nitrile nitrile enolate 3 2 3 () 2 3 2 2 2-2 carboxylic acid carboxylate anion protonated carboxylic acid carboxylate dianion y:\files\classes\314\314 pecial andouts\drawing 2D functional groups home.doc
2D structure drawing hem 314 Beauchamp y:\files\classes\314\314 pecial andouts\drawing 2D functional groups home.doc 3 2 3 2 3 1 o amide amide anion protonated amide 3 2 3 3 () 3 2 2 3 ester ester enolate protonated ester
2D structure drawing hem 314 Beauchamp y:\files\classes\314\314 pecial andouts\drawing 2D functional groups home.doc 3 l 3 l 2 l acid chloride acid chloride enolate (unstable to elimination, forms ketene) l poor due to inefficient overlap of 3p chlorine orbital with 2p carbon orbital l l l l l 6 5 3 6 5 2 6 5 2 6 5 2 2 more times (around the ring) 2 more times (around the ring) 2 more times (around the ring)
2D structure drawing hem 314 Beauchamp 3 2 F 3 F 3 F F use zig-zag drawing for sp 3 chains fluoroalkane F F F till to do. 6 5 3 6 5 2 6 5 2 6 5 2 6 5 2 6 5 3 6 5 6 5 6 5 2 6 5 3 2 F 3 F 3 F F 3 2 3 2 2 2 3 3 2 3 2 3 2 2 2 2 2 2 2 2 2 3 y:\files\classes\314\314 pecial andouts\drawing 2D functional groups home.doc
2D structure drawing hem 314 Beauchamp antidisestablishmenttarianism - opposition to disestablishmentof a church or religoius body an - ti - dis - es - tab - lish - ment - ta - ri - an - ism Break a complicated problem down into simpler parts. 3 2 ( 3 ) 2 2 2 2 2 2 ( 2 ) 2 () 2 () 2 2 6 4 2 2 ()' 2 3 2 ()' l 2 l 2 ( 2 )' 2 ( 3 ) 3 3 3 ( 3 ) 2 ( 2 3 )' 2 2 2 3 ( 2 3 )' 3 2 ( 3 ) 2 2 2 3 ( 3 ) 3 () 2 3 3 6 4 () ( 3 ) 3 2 ( 2 )' 6 5 6 4 3 2 2 3 3 y:\files\classes\314\314 pecial andouts\drawing 2D functional groups home.doc
2D structure drawing hem 314 Beauchamp y:\files\classes\314\314 pecial andouts\drawing 2D functional groups home.doc ' ' l l ' 3 ' 3 ' 3 3 3 ' ketone alkene nitroso nitrite alcohol azide diazonium aldehyde alkyne nitro nitro alkyne alkyne nitrile ester ketone alkene alcohol carboxylic acid alkene alkene nitrile alkyne nitrile thio ether / sulfide amide sulfonamide sulfonamide amide ether ether amine t-butyl ester methyl sulfonate amine thio ether sulfide thiol acid chloride sulfonyl chloride thiol alcohol carboxylic acid sulfonic acid alcohol aldehyde aldehyde ketone