EMISTRY 104 elp Sheet #1 hem 103 Review (Text: h 6, h 7) Do topics pproprite for your lecture Prepred y Dr. Tony Jco http://www.chem.wisc.edu/res/clc (Resource pge) Nuggets: Electronegtivity (6.7), Bond Polrity (6.7), Lewis dot structures (6.2), Bond rder (6.3-6.5), Resonnce (6.9, 7.2), VSEPR (7.2), Bond ngles (7.2), Moleculr Polrity (7.5), yrid ritls (7.3), Intermoleculr forces (7.6), Soluility/Misciility (13.1) ELETRNEGATIVITY: The degree to which n tom cn ttrct electrons in ond. The greter the electronegtivity (EN), the greter the "pull" n tom hs on the electron pir. (The EN vlue of plces it pproximtely etween B nd on the Periodic Tle.) Trend: Increses towrd F. incresing up nd to the right TYPES F BNDS Nonpolr ovlent: equl shring of e - etween two identicl nonmetl elements (e.g., 2, nd l 2 ). Electronegtivity difference is zero (DEN = 0). Polr ovlent: unequl shring of e - etween two nonmetls (e.g., F nd º). Electronegtivity difference is smll (DEN is smll). ΔEN = EN 1 EN 2 with EN 1 nd EN 2 the EN for the 2 toms in the ond BND PLARITY: s the 2 toms get frther prt on the Periodic Tle Þ DEN Þ ond polrity Polr ond: A ond in which electrons re pulled to one side of the molecule yielding slight positive chrge on one side (d + ) nd slight negtive chrge (d - ) on the other side of the ond (d - is with the more EN tom). The polrity vector points towrd the more negtive side of the ond (tom with greter EN): d + d - LEWIS DT STRUTURES 1. ount vlence electrons 2. Drw skeleton structure 3. Build octets 4. heck numer of electrons drwn; if equls the #vlence e - in Step 1 Þ done. 5. Too mny e - Step 2 & dd multiple ond; Too few e - dd electron pirs to the centrl tom. For orgnic molecules, connect toms together nd mke sure the #onds is correct s remining toms re ttched: = 4 onds; N = 3 onds usully; = 2 onds usully; = 1 ond BND RDER (B): Single ond Þ B = 1; Doule ond Þ B = 2; Triple ond Þ B = 3 Bond rder Þ ond strength nd ond length Bond rder resonnce = #onds involved in resonnce #loctions onds involved in resonnce re distriuted Resonnce nd Resonnce Structures: In hem 103/104 resonnce structures typiclly hve doule onds nd n equivlent loction for the doule ond to move to; importnt structures: Benzene, 6 6, B = 9 onds/6 loctions = 1.5: - R R roxylte, 2 -, B = 3 onds/2 loctions = 1.5: -
VSEPR (7.2) (Vlence Shell Electron Pir Repulsion) 1. Drw correct Lewis dot structure. 2. Determine #Domins = #lone pirs of electrons round centrl tom + #toms onded to centrl tom 3. ompre to tle elow. VSEPR Totl = #toms onded # lone pirs on Electron region ERG Picture Moleculr MG Picture Angles Ex Polrity A + B = domins to centrl tom A centrl tom B geometry (ERG) geometry (MG) 2 2 0 Liner Liner 180 o Bel2 NP* sp 3 3 0 Tringulr plnr 2 1 Tringulr plnr Tringulr plnr 120 o BF 3 NP* Bent <120 o AlF2 - P 4 4 0 Tetrhedrl Tetrhedrl 109.5 o 4 NP* 3 1 Tetrhedrl Tringulr pyrmidl <109.5 o N3 P 2 2 Tetrhedrl Bent <109.5 o 2 P P = polr molecule; NP = nonpolr molecule * = The nonpolr (NP) molecules ssume the toms round the centrl tom re the sme; if not, the molecule will e polr Imges: Imges: Pulic Domin from Wikipedi.org (http://en.wikipedi.org/wiki/vsepr_theory) YBRIDIZATIN (7.3, 7.4) + + + + + sp + sp sp 2 domins sp hyridiztion s oritl + p oritl 2 sp oritls liner (180 ) 3 domins hyridiztion s oritl + two p-oritls 3 oritls tringulr plnr (120 ) 4 domins hyridiztion s oritl + three p oritls 4 oritls tetrhedrl (109.5 ) Sigm (s) Bond: This ond lies on the internucler xis etween the nuclei. All onds (single, doule, triple) contin s ond. Sigm (s) onds in this course re usully creted from the overlp of two hyrid oritls,, (e.g., ) or 1s nd hyrid oritl, 1s, when is prt of the ond (e.g., 3 ). Pi (p) Bond: This ond does not lie on the internucler xis, nd is present with doule nd triple onds. z y z y y y x + x x p Pi (p) onds re mde from overlp of 2 p-tomic oritls; p p z p z π ond Single ond = s ond; Doule ond = s ond + p ond; Triple ond = s ond + 2p ond
INTERMLEULAR FRES (7.6) (IMF): Forces etween molecules, not within molecule. -onding: riteri: onded to N,, or F; look for groups; exmples: 3 (l) (lcohols); 2 (l); 3 (l) (croxylic cids); 3 N 2 (mines); -onding IMF re usully stronger thn Dipole-Dipole nd LDF. :.. :.. Dipole Dipole: riteri: polr molecule; exmples: F l or F Br; Polr molecules: o ditomic X Y o compounds with cronyl group (see digrm) o chemicls with,, S, N, nd P o VSEPR Tle: 2 0, 3 0, 4 0, 5 0, 2 3, 6 0, 4 2 with different toms round centrl tom o VSEPR Tle: 2 1, 3 1, 2 2, 4 1, 3 2, 5 1 lwys polr Nonpolr molecules: o ditomic X X o ydrocrons ( x y ) o VSEPR Tle: 2 0, 3 0, 4 0, 5 0, 2 3, 6 0, 4 2 with sme toms round centrl tom re nonpolr London Dispersion Forces (LDF) = Induced Dipole = Instntneous Dipole: riteri: hs electrons; occurs in ll molecules nd individul toms; cused y electrons shifting to one side of the molecule/tom creting n instntneous dipole within the molecule; hydrocrons hve only LDFs #e - Þ LDFs DETERMINE WI MLEULE AS LARGEST IMFs If two molecules hve the sme IMFs (i.e., oth molecules hve -onding or only Dipole-Dipole or only LDFs) determine which molecule hs greter IMFs s follows:. -onding: 1. More toms onded to N,, or F toms Þ more -onding Þ lrger IMFs. Dipole-dipole: 1. Polr ond hs greter DEN Þ greter permnent dipole-dipole Þ lrger IMFs c. LDFs: 1. one molecule is lrger Þ more electrons Þ greter LDFs Þ lrger IMFs 2. hydrocrons: one hydrocron molecule is less rnched Þ greter LDFs Þ lrger IMFs IMFs Þ generlly -Bonding > Dipole Dipole > LDF IMFs Þ Boiling Point ; Melting Point ; D vp SLUBILITY: Liquids dissolving into liquids = misciility (pge 565-567): In generl: Like likes Like polr sustnces dissolve into polr sustnces (dissolve = miscile); nonpolr sustnces (e.g., hydrocrons!) dissolve into nonpolr sustnces (dissolve = miscile); polr nd nonpolr sustnces don t dissolve into one nother (don t dissolve = immiscile) more -onding regions Þ more polr Þ more solule in wter 1. Wht is the electron region geometry nd hyridiztion round the old underlined tom of the molecules elow? (int: Drw the Lewis dot structure for ech molecule.). 4. 3 3 c. 2 2 d. º
2. Drw Lewis dot structures for ech of the following molecules. rgnic structures will usully hve the following onding: 4 onds; N 3 onds; 2 onds. 2 6. 2 4 c. 3 2 d. 3 2 2 3 e. 6 6 (enzene = 6-memered cron ring) 3. I. Which molecule elow hs the strongest ond? (int: Drw the Lewis dot structure of ech molecule) II. Which molecule elow hs the longest ond?. 3-2. 3 2 c. d. 2 ( is centrl tom) e. Sme strength/length. 4. Identify the polr regions in this molecule y leling toms of the molecule with d - nd d +. 5. Answer the questions elow out the structure nd onding in this molecule. (int: Drw in the lone pir e -.). Wht is the ngle etween the -- leled with n?. Wht is the electron region geometry round the cron tom leled? c. Wht is the moleculr geometry round the oxygen tom leled c? d. Wht is the hyridiztion of the cron tom leled? d e. Wht oritls overlp to mke the ond etween the cron tom leled d nd the ttched hydrogen tom? f. Wht oritls overlp to mke the pi (p) ond etween the cron tom leled nd the oxygen tom ttched to it? c g. Wht is the electron region geometry round the cron tom leled d? h. ow mny lone pirs of electrons re there in the molecule? 6. Answer the following questions for the molecule to the right.. Drw in the lone pirs of electrons in the structure.. Wht is the ond order for the ond leled? c. Wht is the hyridiztion on the S leled? d. Wht is the ngle for the on the leled c? e. Wht oritls re used to form the ond leled e? f. ow mny s nd p onds re in the molecule? g. Wht is the electron region geometry round the S tom leled? h. Wht oritls re used to form the onds leled? 7. For ech set of chemicls, order them from lowest to highest oiling point. I. 4, 3 8, 2 6 II. 3 2 Br, 3 2 F, 3 2 l III. 2, 3, 3 3 8. Plce the molecules in order of most solule to lest solule in wter. I. 3 2 2 II. 3 2 2 2 2 3 III. 2 2 e N S d c
ANSWERS 1.. tetrhedrl, {from LDS: hs 4 domins Þ tetrhedrl nd }. tetrhedrl, {from LDS: hs 4 domins Þ tetrhedrl nd } c. tringulr plnr, {from LDS: hs 3 domins Þ tringulr plnr nd } d. liner, sp {from LDS: hs 2 domins Þ liner nd sp} 2... c. d. e. 3. I. c {B = 3 for structure c} II. {B = 1 for structure } 4. The higher electronegtivity of the toms pull the electrons towrds those toms nd concurrently cretes positive region t the nd toms tht re ttched to the toms. 5.. 120 {3 domins Þ tringulr plnr Þ 120 }. tetrhedrl {4 domins Þ tetrhedrl} c. ent {4 domins Þ 2 toms + 2 lone pirs Þ MG = ent} d. {3 domins Þ } e. s: 1s() () {single ond Þ s ond; s onds mde from or -1s usully; hs 3 domins Þ ; s ond = 1s() ()} f. p: p() p() {ll p onds mde from overlp of p-oritls; p ond = p() p()} g. tringulr plnr { toms hs 3 domins Þ tringulr plnr} h. 6 {see digrm} d c δ δ+ δ δ+
e N S c 6... 2 d {doule ond with no resonnce Þ ond order = 2} c. {4 domins round S Þ } d. <109.5 {round the vertex tom ( tom) there re 3 domins Þ tetrhedrl Þ 109.5 } e. 1s() (N) {single ond Þ s ond; s onds mde from or -1s usully; N hs 4 domins Þ ; s ond = 1s() (N)} f. 22s, 2p {single ond = s ond; doule ond = s + p ond; triple ond = s + 2p onds} g. tetrhedrl {4 domins round S Þ tetrhedrl ERG} h. p: p() p(); s: () () {doule ond = s + p ond; s onds mde from or -1s usully; ech hs 3 domins Þ ; s ond = () (); ll p onds mde from overlp of p-oritls; p ond = p() p()} 7. I. 4 < 2 6 < 3 8 {s mss or #e - Þ LDF Þ IMF Þ oiling points } II. 3 2 F < 3 2 l < 3 2 Br {s mss or #e - Þ LDF Þ IMF Þ oiling points } III. 3 3 < 3 < 2 {IMFs Þ Boiling Point ; 3 3 hs dipole-dipole IMFs; 3 hs -onding; { 2 lso hs -onding nd hs 2 toms tht cn -ond, so it hs greter -onding while 3 only hs 1 tht cn undergo -onding; 3 3 hs no -onding, is polr nd hs dipole-dipole IMFs which re in generl weker thn - onding nd therefore hs the lowest p; 3 is next ecuse it hs -onding ut less -onding thn 2 ; 3 3 < 3 < 2 } 8. most solule to lest solule in wter: III > I > II {Wter is polr nd sustnces tht re polr will e solule (miscile) in wter. Both chemicls I nd III re polr ecuse of the polr groups. Since chemicl III hs two groups it hs more polr regions thn chemicl I with only one group. The sustnce with more polr regions will e more solule in nother polr sustnce such s wter. hemicl II is hydrocron nd is therefore nonpolr nd lest solule in wter.}