Arrow_Pushing_Guidelines

Arrow_Pushing_Guidelines - T i ps f o r ar r ow pushi ng 1...

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Unformatted text preview: T i ps f o r ar r ow pushi ng 1 ) T y p es o f ar r ows – Always be sure y ou use t h e c o r r ec t ar r ows. a) M o v e me n t o f two el ec t r o ns – si ngle-h eaded curv ed arrow b) M o v e me n t o f o n e el ec t r o n – h al f- h eaded curv ed arr ow c) Reac t i o n a rr ow – si ngle h eaded arr ow d) Res o n an ce ar r ow – d ouble h eaded arr ow e) Equilibrium arr ow – f o rward/rev e rse ar r ows 2 ) El ec t r o n m o v e me n t is drawn fr o m a n e l e c tr o n s o u r c e t o a n e l e c t r o n s i n k . T h e a rr ow t ail s h ould be a t t h e el ec t r o n s ource and t h e ar r ow h ead sh ould p o i n t t o t h e elec t r o n si n k . a) Co m m o n el ec t r o n s ou rces: l o n e p ai rs o r σ/ π b o nds. I n gen eral , nucleo p h iles t e nd t o be elec t r o n s ources. b) Co m m o n el ec t r o n si n ks: a t o m o r b o nd wi t h i n a m ol ecule t h a t ca n accep t a p ai r o f elec t r o ns i n t h e f o r m o f a l o n e p ai r o r a n addi ti o n al bo nd. In gen eral , elec t r o p h iles t e nd t o be elec t r o n si n ks . 3 ) Co ns erv a t i o n o f c h arge: T h e sum o f all f o r mal c h arges o n i n t erac t i ng m o lecules will n o t ch a nge as t h e resul t o f t h e m o v e me n t o f el ec t r o ns . T h is is a grea t way t o d ouble ch ec k t h a t y ou h a v e n ’ t missed an y t h i ng ! 4 ) Res o n a n ce: I n v ol v es t h e m o v e me n t o f two el ec t r o ns (si ngle-h eaded curv ed arr ows). Usually i n v ol v es p o rbi t als (i .e. t h e m o v e me n t / crea t i o n o f l o n e p ai rs o r pi b o nds.) 5 ) Co m m o n er r o rs a) Backwards ar r ow pushi ng – a rr ows goi ng i n t h e wro ng direc t i o n . b) No t e n ough ar r ows – ar r ows sh ould foll ow each o t h er p recisel y , wi t h ou t s ki p p i ng o r assumi ng t h a t a n y el ec t r o n m o v e me n t is unders t o od. c) L osi ng t rac k o f t h e o c t e t – n o 2 n d r ow a t o m will h av e g rea t er t h a n 8 el ec t r o ns i n i ts v alen ce s h ell . d) L osi ng t rac k o f p r o t o ns a nd l o n e p ai rs . T h is is by n o m ea ns a co m p l e t e se t o f ar r ow pushi ng guidelin es, bu t t h e y s h ould co n t ai n m os t o f t h e i n f o r ma t i o n rel ev a n t t o t h is class. Summarized fr o m: A nsl y n a nd Dough t e r y , M oder n P h ysical Organi c Ch e mis t r y . 2 0 0 6 . ...
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This note was uploaded on 11/07/2009 for the course CH GenChem taught by Professor Mccord during the Spring '09 term at University of Texas at Austin.

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