organo final (unit 3)

Question 1

what is the process for carbonylation of methanol to make acetic acid

Answer 1

CH3OH + CO -> CH3COOH
use cat (grp 9/10 w I)

Question 2

how do you make methanol

Answer 2

CO/H2 + het-cat

Question 3

how do u make CO

Answer 3

CH4 + 1/2O2

Question 4

List the three cats used in carbonylation

Answer 4

BASF - Co, I-
Monsanto - Rh, I-
Catvia - Ir, I-

as you move down, better activity and selectivity

Question 5

draw out the Monsanto cycle (include names of steps, co cats, precat, TLS, complexes, and imp notes)

Answer 5

see notes
TLs - OA (polar, stepwise)
Rh anion makes good nu and suscept to E+ addition of Me+

Question 6

what is TLS for catvia process and why/not

Answer 6

not OA of MeI bc much faster for Ir
-form stronger bonds to 3rd row tm
-higher nu of 3rd row tm
-pref for 3rd row tm for high os

mig insertion of CO
-formation of stronger bonds to 3rd row tm bw Ir-Me
–the E barrier changes for the M-L ligand to act as a nu to Carbonyl C

Question 7

what can be done to speed up TLS for catvia process

Answer 7

add promoter (Ru dimer); accel negated by I- and Ru accepts I- and gives neu fac-tricarbonyl complex

-neu increases how sus co is to nu attack
-xtra co compete
these 2 things make co more E+ t/f increase rate of nu attack (intra)
–both make lead to less backbonding from M, t/f CO lig becomes more E+

see notes for process and dimer

Question 8

what is the process for catalytic hydrogenation

Answer 8

alkene + H2 -> alkane w syn H’s
use cat

Question 9

what are the cats used in hydrogenation

Answer 9

wilk - RhCl(PPh3)3
[Rh(dppe)(solv)2]+
[Ir(COD)(py)(PCy3)]+PF6 (crabtree)

all do H first
have labile lig’s

Question 10

draw hydrogen first mech (inner or outer?)

Answer 10

inner

see notes
2 vac coord sites, oa H2, lig assoc, 1,2 ins (TLS), RE

Question 11

draw olefin first mech (inner or outer)

Answer 11

inner

see notes

cats: Ru(H)Cl(PPh3)3
Cp2LaH

M-L and -H, lig sub (alkene for L), 1,2 ins and lig assoc 9L), oa H2, RE

OA and RE = hydrogenolysis

Question 12

draw the cycle for hydrog of ketones(list steps, ts, imp notes)

Answer 12

see notes

outer
H first(attach to M and L in 4Cts)
then lig assoc of ketone (get ts w H’s)
-this ts is prochiral (if reduce it, it will become chiral)(has enentiotopic face)
(which 1 binds dets enant formed)
then dissoc?

Question 13

draw cycle for hydrog of ketones using OH, not H2

Answer 13

see notes
outer
lig assoc of alc, then ts w it’s H’s
ketone leaves then re-assoc’s
leave w same alc SM but now enriched

Question 14

overall process of hydrosilation

Answer 14

alkene + H-SiR3 -> alkane w h and SiR3 syn
use cat
HSiR3 = reducing agent like H2; NP and bulky

Question 15

what is used in hydrosilation and what do they rely on

Answer 15

Pt, Rh, lanthenides
which all rely on activation of Si-H bond by M and 1,2 ins step
-use anti-mark addition - Si on least hindered end of alkene

Question 16

draw the two mechs of hydrosilation for Pt and Rh

Answer 16

see notes

Pt: mig ins of olef into MH
Rh: mig ins of olef into SiR3
like chalk harrod

Question 17

draw mech of hydrosilation for lanthanides

Answer 17

see notes

usu d0 t/f do sig-bond-met
start w precat (Cp2Y-Ch(TMS)2)
add H3SiR (4cts)
left w Cp2Y-H (act cat)
do lig assoc of alkene and 1,2 ins
add H3SiR (get 4cts)
spits out RH2Si -alkane

Question 18

what does asymmetric mean

Answer 18

aka stereoselective

a rxn that yields increased amnts of 1 stereoiosomer rel to other poss’s

-rxns that reduce db’s can gen enantiomer’s when unsat’d sub is prochiral, if reduction occurs stereospecifically

Question 19

what does a prochiral olefin have

Answer 19

enantiotopic faces
-2 enant’s form when bind to M, dep on which face approaches the M

-if Mln = achir=get enant complexes
-if Mln = enant pure L=get diast

Question 20

what are some key aspects of asym hydrog of alkenes w Rh(I) cations

Answer 20

alkene 1st
subs may have D grp that can bind to Rh to help ensure alkene anchored to bind to correct place

act cat = [Rh(solv)2(diphos)]+

chirophos = used to make an alpha aa deriv; has c2 sym
chiral and chelating phos’s used to make hydrog enantiosel

Question 21

draw cycle for asym hyd of alkenes w Rh(I) cations

Answer 21

see notes

cat precursor (w COD; add 2H2 + 2S to get rid of octane)
lig assoc
OA H2
lig assoc and ins
lig sub

Question 22

which product gets formed when using [(chirophos)]Rh]+

Answer 22

more stable and abundant interm gives minor prod enant
-poss bc fast interconversion bw diast’s

Question 23

explain the curtin-hammett principle

Answer 23

when competing rxn paths start from rapidly interconverting isomers, the product ratio is det’d by rel deltaGTSsymbol (ie rates/rate constants/barriers) leading from isomers to products

have plot E x rxn coord
in middle can interconvert bc small barrier when alkene approaches
-facile and fast eq

can go L or R but OS of H2 is going to be lower E for one of the ways which will be fav’d

–less stable isomer reacts faster t/f leads to major product (lower E barrier)

Question 24

what is overall rxn for pd cross coupling

Answer 24

alkene - X (w sp2C) + R-M+ -> alkene - R + MX

-for CC bond formation
-subs = aryl, vinyl, pseudohalide which act as cat nu (R)
-main grp (M) = Mg, Zn, Sn, B, Si

pd = usu cat

Question 25

draw the cycle used for suzuki-miyaura, stille, hyiyama, negishi, kumada

Answer 25

suz- B
stil-Sn (tin)
hiy - Si
neg - Zn
Kum-Mg

see notes
get to reduced Pd 0, then lose L to get 1-2 L in act cat
ArX OA
Transmetallation
RE Ar-nu

Question 26

draw cycle for mizoroki-heck

Answer 26

use when other’s arent present

see notes (2 cycles)

Ar-X + alkene -> Ar -alkene + HXbase
use Pd cat and base

Ar grp ends up on least sub’d

same as other mech’s but do 1,2 ins, then Bh elim and RE of baseHX

Question 27

xtra notes ab suzuki-miyaura

Answer 27

B(OH)2
also use base
-hard like OH or F which is needed to facilitate cross coupling
i)4 coord anion [ArB(OH)3]- may transfer Ar gpr faster than ArB(OH)2
ii) OH- replaces Pd-X, so Pd-OH participates more easily in transmet.

rel rates of OA: arI>arbr>arcl and artf>Arots

Question 28

what is the overall process for olefin metathesis

Answer 28

2 alkene (2R1 and 2R2) -> 2 alkenes (allR1 and all R2)
use cat (usu alkylidenes like schrock carbenes- M=CR2)
-can use grubbs which still have schrock aspect but also bulky lig and/or strong sigma donor’s like PCy3 or NHC’s
–5 coord sq pyram

lose ethylene = DF

Question 29

what transformations are possible w olefin met

Answer 29

RCM, ROM, cross met (two alkenes merged to 1), acyclic diene metath

Question 30

mech of olefin met

Answer 30

see notes

metal d-orbs in M=C bonds allows transformation of 2+2cycloadd (usu forbidden for C=C bonds)

start w alkylidene, lig assoc of alkene and 2+2 cycladd, 2+2 cycloadd and lig dissoc, repeat for second alkene

Question 31

synthesis of schrock carbene

Answer 31

alpha - elim from dialkyl precursor
see notes

Question 32

Justify why OA is not RDS when using Ir in hydrogenation

Answer 32

1. Ir is larger than Rh and less charge dense t/f better nu for E+ Me t/f increases RDS
2. 3rd row TM create stronger M-L bonds
   -stronger bond being form lowers TS E (thermo feat)
3. TM’s in higher OS are more common for heavier TM’s (comp’d to lighter)
   -rationalized by charge-density argument (higher charge spread over larger radius)

Question 33

what are examples of additives in Pd cross coupling

Answer 33

bases (K2CO3)
M-halides (CuCN)

Question 34

what makes an alkene more susceptible to nu attack

Answer 34

EWG (like H or CN or COOR)

Question 35

how to make organo borane

Answer 35

2 methods (see notes)