Question

Since we haven't yet covered this in class, your class textbook may be a valuable source of information in helping to answer these questions. 1. Using the generic chemical species below (E = eletrophile/substrate, LG = leaving group, and Nu nucleophile), show the mechanism (adding curvy arrows/showing electron movement) for both an S, 2 and an S, 1 reaction. Be careful with charges as bonds are broken and created. Also notice that the nucleophile for the S.2 reaction has a negative charge, while the nucleophile for the S.1 reaction does not SN2 Nu E-LG [SNI Ňu E-LG

Answer 1

ANSWER-5.
- Nul .. (95) (ts). 'e' iu ground stäté į sp while the 'c in transition state is oper. In qo, le is tebiñ co-ordinated and in ts, 'e' å benta - co-ordinated . . e in its' is more congested than the in got. If the as į congested itself then its ts. becomes congested t o a great excelent to becomes highly unstable and the FA increases thereby making 5M² unfavourable. Let us consider the 3 alkyl hallides- Rate of SNI decreased CA) ен, — Bн ; (б) нь он — (o) e-Box (2) Rate of SN² decreases. from left to right , congestion of gs increases and that of ts. increases bremendously. Its š going l ê be extremely unstable. 8. Sy² sesen becomes unfovourable pe In gg diff. is less as ne iš tebia - A Co-ordinated In ls. diff. is more as pe e is perla co-oqdinated. 18+ ۱۴ هے

IN 1 7 However for the same alkyl hallides the state of ONA - gradually increases from left to right. Sn' has 2 ! steps among which step-1 is the ads. In the first step, carbocation is formed and the to i car boeation like. The more slable " th m ere stable is the 'to. . EA decreases, i. 9x² SN ecomes much more stable A, B il forms 1, 2, 3° May bocation respectively. 3oygoy 1° → acc. l ê stability
Now since the given molecule is a 3 degree one hence SN1 will be favoured for it.

ANSWER

1.For SN2 REACTION-

VBT- NU XV to No such repulsion .k I bo more Ž box zunilor changer is élose huult leading i aleatione repulsion! o less stáble flâble. Humid H H (5.5) # (Pdt) +X-) { Learing group) 7.s. - earm stable. Rx" wantê lê proceed through this T. i. Backside approach is much more favourable. than froutside approach. But this is according to Valence Beud ! Theory and hence obsoletê . According l ů I MOT - Nucleo fhile ě nucleus - loving and hence é fair doner i.e. it has t o be either an aniowie Leg. OH) or a neubial 1 & fecies (H₂O, PH₂, elé. ). Let us consider NH₂ for the same rxn. A neutral nucleo phile donates its lp lo Participate in such ox". The ersch. then does not follow the above concept. This is because i ť anione species reacts it becomes neutral but a neubial species donales e lo form catione species. The oth is as follows above.

FOR SN1 REACTION-

Let us consider the following molecule - Nefy Heny Nun while studying the kineties of this arsen, if the care of Nu i r fixed dosen rate raries. But if the substrate & " Nu { varied then the lisen rate does not vary. This proves that the door å net SN² type of disen • Rale = K |CHg), L-X1 The arren, follows 1st order. Hence it ů named as substilulrón Nucleofhile Urimeleculay ( 5N1). The unis met Sungle step as there are 2 reactants is only 1 of them is involved in ords. so there must be 1 more slep. where Nu is involved. In the 1st step of this ex- leaving group leaves the system taking the bonded e-pair of the bond with itself and a carbocation is formed In the 2nd step tu attacks the " and we get the corresponding folt. Since there are 2 steps - formed.

which slowest oclet is the rids ? step as it configuration. " Obriously the 1st step as it is the forms a cay bocation (sextálé ) from the In the 2nd step " it si a fast step. The mechanism is as goes t Lollowed - e 74) CHy xH #fit Nu him Helm Nu (-) the energy profile diagram å as follows - TS-1 To-2 R-Nu. decording t alike that Here Tos. o Hammond's pertulate which states that TS will look particular state t o which it ů energétically cleser. is closer t o the intermediate T.S! →
3.SOLVENT FOR SN1 REACTION-

4.SOLVENT FOR SN2 REACTION-

INA AXn has a steps but we are concerned with the 1st sef only as it is the rids. So as involves only the substrate where no change is there. But in the TS there are partial charges... TS i more folar / than gs. If the polarity of the solvent u + increased, Ts & more stabilised than gs. . EA decyeases and the siden, becomes favourable. TS KEA

We knew SNO sro", ù more favoweed en less felar &olvent and 5N1 " " " " " mere " " . By the term fuetie selvent we mean a selvent that can take part in H- bonding sp aprette qs elvent å " " " " not .. . g. doethyl etherego preté > 40 If a solvent ů folar and it has to bouding ability then it ů called polar foreto velrent. If a pelvent ů pelar with no such ability it is "apuatie ". SN2 In the ground state of the reactant there was no change on any atom of the subsbiate ! Nu had a cone discuelê ve charge! In the TS no new change is added 'but the existing of Nu is dispersed through 3 alims. oo gs is more falar than to as in to the change density is much less than that in goooo go is more & labilised in polar solvent than th. The energy gap between go & TS is the energy of activation between them. The energy gap neyeases with increase in folarity of the selvent." oo the sean becomes selvent. 1 I IS . 1 1 PM PoE 6515 To However & Nu or substrate in Partial charges. New pelarity of pelvent than go. : EA ý neutral then there i no change in Nu the go. But in to there exerti To is mere polar than go. of i increased to is more stabilised decreases . . SN² sx", befones feasible.

5.