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UCO / Chemistry / CHEM 3323 / In chemistry, what are alkyl halides?

In chemistry, what are alkyl halides?

In chemistry, what are alkyl halides?

Description

School: University of Central Oklahoma
Department: Chemistry
Course: Organic Chemistry II
Professor: New
Term: Fall 2016
Tags: organic and Chemistry
Cost: 25
Name: Ch. 7 Review for Org Chem II
Description: These notes cover SN1 and SN2 reactions, as well as chirality centers, reaction profiles, nucleophiles, and leaving groups.
Uploaded: 08/28/2016
7 Pages 57 Views 2 Unlocks
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o E


In chemistry, what is alkyl halides?



-

Ch. 608;4

Org I Keview

Dr. New

Substitution Reactions by one group is exchanged for another Lelectrophile = substrate, must contain

leaving group

* the leaving group can stabilize charge o alkyl halides : Naming.

bu halogens are named as substituente. Ist sub. is lowest

numer on parent chaen as possible. b Remember stereochemistry! *Chirality center

Cp.289)06.203-20) )-5-fluoro-2,2-dimethylhexar

@ beginning conoch

If multiple (ar,s)... etc highest atomic # (size) = highest priority I always lowest, on dash 11119 left (s)


What is the polar aprotic?



-5-fluor

Och5 {chirality) highest

MOH

C

BUDI

CH

H

higher priority :C >H

H

look for 1st point of difference a double bond is considered two seperate singl bonds , 0 counts for any If you want to learn more check out What is the study of anatomy?

o multiple bond IH

Newman * Use a model kit to practice!

1.1.d. the 4 atoms directly attached to chirality center: 1 projections 2. Assign a priority to each atom.

Ch. 4 3. Look for the first point of difference. 4. Rotate so that lowest priority is in back.


Carbocations are subject to?



Two chirality centers: 5. Determine (R) or (S).

Enantiomers o Diastereomers

Oom each stereoisomer XX AS has one twin

in . w and two other same

different

siblings Non superimposable ImireaD imalne

different Don't forget about the age old question of What is a hydroxide?
If you want to learn more check out Why did the ming need the europeans?

Set 1

Set 2

Naming

a Carbon

2

Study SOUP

Possible mechanisms for Substitution Reactions

Steps 1- Nuc. attack 2. LLC 3. PT Y.OR

Lo every substitution has at least two patterns

Lo is it simultaneous concerted or stepwise?

[1'>2°>30]

occurs at once

I NR

logooo strong> COREZ)

SNa

- SNI Svi /unimolecular'} .nuc@attack +ula If you want to learn more check out What is the bone structure of the earliest bird like fossils such as archaeopteryx?

RDS (LLA) LoL 302301

• carbocation

•nuco attack (weak a 1 ogood LG base)

ogood nucoli weak base (good LG

weak nucleophile

(weak base) Cor El) Sterics

A confirmation

Tho st) (nuco can only 2 CS --R) (inversion] attack from back A reactant product

"Umbrella flip"

HS--- ----Br: [p.297] Dare l Ÿ Ét bigger = Slower

group leaving Los similar to 3o

rearing

nuco

attacking

SNI: stepwise

LRDS: formation of carbocation by loss of leaving group

e intermediate) nudeophilic attack on carbocation intermediate.

intermediate is planar: nuc. must attack If you want to learn more check out What are the difference between transmission electron microscope from scanning electron microscope?

from the front or back

17.a

INAC

rate= k[substrate ], 1st order, unimolecular We also discuss several other topics like When was the science of forest soils began?

* Mechanism must exhibit a rate-determining step

where nucleophile doesn't participate. * Unimolecular: only one chemical entity participates

in RDS s rate is not affected by nucleophile. * Rate only dependant on leaving group leaving. Structure

Sna: steric hinderonce (3°) - nuc. has to directly attack substi SNI: nuc.doesn't attack substrate directly - carbocation

intermediate and it's stability (30) undergo Swi.

* SNI or SN2 FOR. 2°!)

* Sna = inversion

SNI 2° SNI 30 SNI retains configuration and iwerts (50/50 SIR):

Soup

L attack front or back

Complete mechanism of SNI]

1. Coss of LG

to TT

StSoup

2. Auc. a face * 3. Proton Transfer z can occurs before I between Jafter 1/2 * 4. Rearrangement »

SoH is bad 1.9., will Necessary for ALCOHOL SUBSTRATES / not leave on its own. in OH is only 6.g., acidic (HR) conditions are required to

protonate. (Exi HCI supplies H30*) aikyl halides have good leaving groups.

o

© Additional steps for SN 2

* Proton transfer before nuc. attack + loss leaving

group (concerted) * required at beginning if substrate is an ALCOHOL

COH is bad wearing group * Proton transfer at end if nucleophile is neutral Cremove positive charge from compound -- Ex:

H20 deprotonates H30+) slike sna which predominates? SN or swa?

1.

SNI

SN2

( methyl I

CSN2) inversion, racemization (SNI) E @ chirality center CSNIS rearrangement, not possible CSN2) = substrate susceptible

to rearrangernent? *Trends (Fig. 7.25 pg.321)

allylic and benzylic

halides SN2 or SNI

Ax

po 20 30

10 20 30

unhindered

resonance-stabilized Steric hinderance

Carbocation

carbocation Stability

Platon

spa ØSNZ

* vinyl laryl halides are unreactive 11x

Lloss of leaving group generates 1

unstable carbocation.

Le Study Sour

* Solvent can act as nucleophile.

bilf nucleophile is neutral C like H2O), there is a

proton transfer at the end of the mechanism. solvolysis

hy tö-me

Mer

for me

su

me

Iloss 1.9.

OCI

Study so

4K:o

proton

transfer

meroit to

Ninc. attack * carbocations are subject to rearrangements Chydride/methyl

bo shift to î stability (2°~3°) if possible

to rearrangement then nuc. attack Speed of rearrangement determines product distribution/

-

Î PT 40 : CRNA

PT

PE

Rxn coordinate

base

S

SNI

omethyl and 10 : SN2 * 30 : SNI .2°) allylic or benzylic either SN2 or SNI

• Vinyl and aryl do not react via either mechanism The Nucleophile!

Common nuc's

IO . Strong - SNa

Tro I want weak

HSO HOO

cweak = SNI

Bro H2S Roo | H2O CHORSH NEC LROH nuco donates eo

C STRONG Weak base) Examples

SN2

non nys) no NaOH) NaN)

• weak

ostrong • strong strong strong

•SNI

•SN2

SN2 SNZ SN2 the Learing Group

· SNI: LG must be highly stabilized Cconjugate base of Starting acid)

o weak bases are highly stabilized SA - WB

OOH is not a stabilized CB : Bad CHCI) Ccio)

leaving group. COH = strong base) ACID

Ceaingate Base strongest Acid

I-H

IC

Bre

이내

Study Son

Most STOBLE

mo

Br-H

CIO

L.G.

SO

HH

Study Soul 14

-

-

-

-

-

-

--

--

Ное

H2O OH

Bad L.G.

NHO

ankest

Treast stable w/

H

©

and SOUL

Solvent Effects

OSNI Hotic - Cprofon) contain at least 1 Hatom

connected directly to the electronegative atom. .SN2 Polar aprotic -no H connected directly to

electronegative atom

• solvent shell holds eo

o solvent affects order of reactivity of halides

ol weakest

|PROTIC I strongest Los Broscio >

nuc.

Fol nuc.

Cleast stable)

DOLAR APROTIC

FO > Clo>Bro> IO

-

pi most - least stable strength P.A.: Least - most stable: strength] most least able to donate eo

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