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Ochem CH16
| Question | Answer |
|---|---|
| Types of dienes | conjugated, isolated, and cumulated |
| Cumulated diene | are not separated by any bond except atom |
| conjugated dienes | are two double bonds that are separated by only 1 single bond |
| isolated dienes | are two double bonds that are separated by more than 2 bonds. |
| what allows better stability for diene structures? | Resonance stabilized, the farther away the dienes are to each other, the less stable they are. Therefore, will release more heat during hydrogenation. |
| When diene reaction is heated what product will occur and why? | The more stable products will be formed after heating, which establishes equilibrium concentrations. this is under thermodynamic control |
| What can prevent a compound from undergoing an Diels-alder rxn? | if needing to take S-cis confirmation but being sterically hindered. |
| Diels–Alder reaction only occurs when | the diene adopts an s-cis conformation |
| Compounds who are permanently locked in an s-cis conformation .... | react extremely rapidly in Diels–Alder reactions: |
| increasing lambda max (wavelength) | The closer the pi bonds are to each other the greater the wavelength max. extended pi systems, the HOMO-LUMO energy gap becomes so small that absorption occurs in the visible rather then the UV region of the electromagnetic spectru |
| lambda max is | wavelength of maximum absorption |
| molar absorptivity | amount of UV light absorbed at the λmax for any compound expressed by the Beer-Lambert law equation |
| What is the starting base lambda max for conjugated dienes? | 217 nm |
| How much is added to lambda max for each additional double bond | 30 |
| auxochromic alkyl groups | +5 nm |
| exocyclic double bonds | +5 nm |
| homoannular dienes. | +39 nm |
| At 0 degrees, | addition reaction is kinetically favored because it occurs faster H is added to 1c and halogen to 2nd C. reaction is irreversible |
| At 40 degrees celcius | Adduct rxn is thermodynamically favored, and forms more stable product, such as 1,4 adduct reaction because it is more substituted. H is added to 1C and Halogen to 4th C, double bond is rearranged. |
| Types of pericline addition rxns | Sigmatropic rearrangement Electrocyclic reactions Cycloaddition reactions |
Created by:
cguerrero8
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