Question

Orgo Lab experiment: Isomerization of Carvone

1. Carvone contains a ketone and two double bonds. However, when treated with the concentrated acid only one reacts to create the carbocation. Which alkene reacts to form the carbocation and why only the one?

2. After the carbocation rearranges an elimination occurs, the alkene formed is a trisubstituted instead of the tetrasubstituted alternative. Why is this odd and what is the driving force for this specific alkene formation?

3. Using the H NMR and IR data given to explain how you can confirm the transformation of carvone into the product.

Please explain in sentences or paragraphs thank you!

% Transmittance 4000 3500 3000 2500 1000 2000 1500 Wavenumbers

Answer 1

PE Isomerization of carbone. 3). .carpone contains.a Ketone and two couble bonds. However treated wah the concentrated acid only one - reacts to create the carlocation.. which alkene reacts to form the carbocation and why only th the one ? Ars In Carnone one allene is conjugated with ketone (celled conjugated enone); other arkene is not conjugated the conjugated alkene is electrophilic because the it is conjugated to the carbonyl group. and other non conjugated alkene is Nucleophilic So the treatment of carulone with concentrated and promotes reaction of with non-conyugated Nucleophilie alkene to generate a Cabocation ISTEP-1 Conjugated Electrophilic ConcH+ akene til cho O in non ing conjugatel Aucleophilic alkene Tertary - carbocation Q. 2) After the carbocation rearranges an Elimination, - occurs. the alkene formed is tisubstituted instead of the tetrasubstituted alternatie. Why is this oold and what is the orming force for this specific alkene formation ? Ans. The tertiary ccirbocation that is generated in STEP-1 Will á undergoes sesarrangement inuolue migration of Hydrogen from carbon 'A' to carbon B This migration of a hydrogen atom cated also called a l, 2hydride shift

STEP=27 Searrangement 1, 2 hydride - sheft The rearranged Carbocation Generdded in STEP-2 Will Eeact to generate coryugded diene. STEP-31 Y & HO A THO Conjugated diene In this step a new pi bond will form with by generating the acid used in step-1 so overall reaction en catalytic... The new alkene formed is toon conjugated with the alkene of the enone functional group, which is more stable than the tertiary carbocation the Conjugated diene will go through onemore step to generate highly stable carnacabl. product 911 16-y emolizohen - YUI > YS oxonium ion cartaceol STEP-4 product In this last. Enolization step ketone is converted to phenol via Proton assisted oxonium ion for intermediate formation 9H00 K arel

9.3) Using the #H NMR and IR Data given to explain how you can confirm the transformation of coryone in the product. ns IN IN NMR for new product carvacrol Will come some new peak in Aromatic region, as well as with Caround 6-7 ppm) as well as phenolic -on proton IH NMR will peak will come around 9-10 ppm: In NMR pata for earsone & carvacrol product. 2.15 .79 in 9.68 6-81 6.351-1 73-2-2 2.06 Y I 4-5-11 7.06 m2 1.79 carvone 6.99 V 12 **667 287 1.2 carvacrol product IR bata for product carvacrole OM feguency Assignment. 3100-3700 - von, phenol 3023 — YCCH, sp?) 2821-2961 - YCch, Sp3) 1502 - 1621 - (CEC.aromar) 1383–1450 - ☺ (crzi bend 1253 - cc-on, preno!