Organic Chemistry I



Download 24,01 Mb.
Pdf ko'rish
bet144/193
Sana20.07.2022
Hajmi24,01 Mb.
#829540
1   ...   140   141   142   143   144   145   146   147   ...   193
Bog'liq
Organic-Chemistry-. print

N
2 Reactions
Strong nucleophiles are required in S
N
2 reactions, and strong nucleophile are usually negatively charged species, such
as OH

, CH
3
O

, CN

etc. These anions must stay with cations in salt format like NaOH, CH
3
ONa etc. Since salts are
insoluble in non-polar solvent, therefore non-polar solvents are not appropriate choices, and we need polar solvents
that can dissolve the salts.
The issue for
polar protic
solvent is that the nucleophile anions will be surrounded by a layer of solvent molecules
with hydrogen bonds, and this is called the solvation effect. The solvation effect stabilize (or encumber) the nucleophiles
and hinder their reactivities in S
N
2 reaction. Therefore, polar protic solvents are not suitable for S
N
2 reactions.
Figure 7.5b Protic solvent does not work for SN2: nucleophile is solvated and
encumbered by protic solvent
7.5 SN1 vs SN2 | 263


As a result the
polar aprotic
solvents, such as acetone, DMSO etc are the best choice of S
N
2 reactions. They are polar
enough to dissolve the salt format nucleophiles, and also not interact as strongly with anions to hinder their reactivities.
The nucleophile anions still move around freely in polar aprotic solvent to act as nucleophile.
The reaction rate for a S
N
2 reaction in different solvents are provided in the table below, and the polar aprotic solvent
DMF proved to be the best choice that speed up the reaction significantly.
reaction
:
CH
3
I + Cl


CH
3
Cl + I

solvent
relative rate
CH
3
OH
1
12.5
1,200,000

Download 24,01 Mb.

Do'stlaringiz bilan baham:
1   ...   140   141   142   143   144   145   146   147   ...   193




Ma'lumotlar bazasi mualliflik huquqi bilan himoyalangan ©hozir.org 2024
ma'muriyatiga murojaat qiling

kiriting | ro'yxatdan o'tish
    Bosh sahifa
юртда тантана
Боғда битган
Бугун юртда
Эшитганлар жилманглар
Эшитмадим деманглар
битган бодомлар
Yangiariq tumani
qitish marakazi
Raqamli texnologiyalar
ilishida muhokamadan
tasdiqqa tavsiya
tavsiya etilgan
iqtisodiyot kafedrasi
steiermarkischen landesregierung
asarlaringizni yuboring
o'zingizning asarlaringizni
Iltimos faqat
faqat o'zingizning
steierm rkischen
landesregierung fachabteilung
rkischen landesregierung
hamshira loyihasi
loyihasi mavsum
faolyatining oqibatlari
asosiy adabiyotlar
fakulteti ahborot
ahborot havfsizligi
havfsizligi kafedrasi
fanidan bo’yicha
fakulteti iqtisodiyot
boshqaruv fakulteti
chiqarishda boshqaruv
ishlab chiqarishda
iqtisodiyot fakultet
multiservis tarmoqlari
fanidan asosiy
Uzbek fanidan
mavzulari potok
asosidagi multiservis
'aliyyil a'ziym
billahil 'aliyyil
illaa billahil
quvvata illaa
falah' deganida
Kompyuter savodxonligi
bo’yicha mustaqil
'alal falah'
Hayya 'alal
'alas soloh
Hayya 'alas
mavsum boyicha


yuklab olish