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<p>Woodward-Fieser Rules - Dienes The rules begin with a base value for lmax of the chromophore being observed:</p><p>acyclic butadiene = 217 nmGroup Extended conjugation Each exo-cyclic C=C Increment +30 +5 Heteroannular (transoid): Homoannular (cisoid):</p><p>Alkyl-OCOCH3 -OR -SR -Cl, -Br</p><p>+5+0 +6 +30 +5</p><p>base lmax = 214 e = 5,000 15,000</p><p>base lmax = 253 nm e = 12,000-28,000</p><p>-NR2</p><p>+60</p><p>Woodward-Fieser Rules - Enones</p><p>b a b C C C O</p><p>d g b a d C C C C C OIncrement Base 215 nm Base 202 nm Base 245 nm 30</p><p>Group 6-membered ring or acyclic enone 5-membered ring parent enone Acyclic dienone Double bond extending conjugation Alkyl group or ring residue -OH -OR -O(C=O)R -Cl -Br -NR2 Exocyclic double bond Homocyclic diene component a, b, g and higher a, b, g and higher a, b, g, d a, b, d a, b a, b b</p><p>10, 12, 18 35, 30, 18 35, 30, 17, 31 6 15, 12 25, 30 95 5 39</p><p>Woodward-Fieser Rules - Enones Aldehydes, esters and carboxylic acids have different base values than ketonesUnsaturated system Aldehyde With a or b alkyl groups With a,b or b,b alkyl groups With a,b,b alkyl groups Acid or ester With a or b alkyl groups With a,b or b,b alkyl groups Group value exocyclic a,b double bond Group value endocyclic a,b bond in 5 or 7 membered ring 208 217 +5 +5 Base Value 208 220 230 242</p><p>3</p><p>Substituent Effects on aromatic compounds</p><p>PrimarySubstituent-HElectron donating</p><p>Secondary</p><p>lmax203.5 207 210 210 211 217 230 224 230 250 224 269</p><p>e7,400 7,000 7,400 7,900 6,200 6,400 8,600 13,000 11,600 11,400 9,800 7,800</p><p>lmax254 261 264 261 270 269 280 271 273</p><p>e204 225 190 192 1,450 1,480 1,430 1,000 970</p><p>-CH3 -Cl -Br -OH -OCH3 -NH2 -CN C(O)OH -C(O)H -C(O)CH3 -NO2</p><p>Electron withdrawing</p><p>4</p><p>Di-substituted and multiple group effects on aromatic compounds</p><p>Parent Chromophore R = alkyl or ring residue R=H R = OH or O-Alkyl</p><p>lmax 246 250 230 Substituent increment</p><p>O</p><p>RG</p><p>o37 11 0 2 13 20 20</p><p>m37 20 0 2 13 20 20</p><p>p1025 78 10 15 58 45 73 85</p><p>Alkyl or ring residue-O-Alkyl, -OH, -O-Ring -O-Cl -Br -NH2 -NHC(O)CH3 -NHCH3 -N(CH3)2</p><p>G</p>
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Woodward-Fieser Rules - Dienes The rules begin with a base value for lmax of the chromophore being. Documents Similar To Woodward Fieser Rules.pdf. Woodward-Fieser Rules. Apurba Sarker Apu. 5 Woodward Rule. Dipti Dodiya. Woodward-Fieser Rule Diene. Slide 5: 5 The Woodward-Fieser rules are designed to predict the absorbance of conjugated systems in the ultraviolet-visible region of the spectrum based on the connectivity of atoms within the system. It is used for finding absorption maxima position (λMax). This may be differs from observed values by 5-6.