Search for notes by fellow students, in your own course and all over the country.
Browse our notes for titles which look like what you need, you can preview any of the notes via a sample of the contents. After you're happy these are the notes you're after simply pop them into your shopping cart.
Title: Alkynes
Description: It includes 1. Introduction 2. Nomenclature 3. Preparation of alkynes 4. Reactions of alkynes 5. Practice questions
Description: It includes 1. Introduction 2. Nomenclature 3. Preparation of alkynes 4. Reactions of alkynes 5. Practice questions
Document Preview
Extracts from the notes are below, to see the PDF you'll receive please use the links above
Alkynes CHE111
2015
ALKYNES
Contents
1
...
1
1
...
2
1
...
3
1
...
4
1
...
5
1
...
When R=R1=alkyl group, the alkyne is called an internal
alkyne
Replace the suffix –ane of corresponding alkanes with –yne to show the presence of the triple bond
Bonding in alkynes is as shown in the figure below
UoE, Dep’t of Chemistry & Biochemistry, rkc, June 2015
Page 1 of 5
Alkynes CHE111
2015
Part a
...
Again, as there is a
portion of s orbital in an sp orbital this bond is referred to as a sigma bond
...
portrays the two p orbitals overlapping to
form the second and third bonds between the carbon atoms
...
And Part c
...
2 Nomenclature
The simplest alkyne has n=2, ethyne (commonly called acetylene)
UoE, Dep’t of Chemistry & Biochemistry, rkc, June 2015
Page 2 of 5
Alkynes CHE111
2015
Number the alkyne parent chain such that the triple bond is given the lowest number possible
Example
3
2
2
1
1
3
5
4
4
6
2-pentyne
3-methyl-1-hexyne
3-methyl-1-butyne
1
...
heat
CaO + C
C2H2
+
Ca(OH)2
From dihalogenoalkanes
Vicinal dihaloalkane and germinal dihaloalkanes give alkynes when reacted with strong bases such as -OH
H H
Br Br
H2O
CaC2
KOH
CH3CH2OH
Higher alkynes can be synthesized from acetylene
...
The pKa of acetylene and
terminal alkynes is approximately 25, which makes them stronger acids than ammonia (pKa = 36) but weaker acids than
alcohols
...
CH3CH2CH2CH2Br
CH2CH2CH2CH3
(Alkylation reaction)
Alkylation can be repeated and a terminal alkyne can be converted to an internal alkyne
UoE, Dep’t of Chemistry & Biochemistry, rkc, June 2015
Page 3 of 5
Alkynes CHE111
2015
1
...
Complete addition to an alkyne will require twice the quantity of halogen (1), hydrogen (2) or hydrogen halide (3)
...
UoE, Dep’t of Chemistry & Biochemistry, rkc, June 2015
Page 4 of 5
Alkynes CHE111
2015
Lindlar catalyst (palladium in calcium carbonate poisoned with lead acetate) leads to partial hydrogenation to yield cisisomer
...
This is called dissolving metal reduction of alkynes
H
H
H
H
H2, Pt
H2, Lindlar catalyst
cis-isomer
Na, NH3
trans-isomer
1
...
What would be the product of adding water to alkynes using HgSO4?
2
...
UoE, Dep’t of Chemistry & Biochemistry, rkc, June 2015
Page 5 of 5
Title: Alkynes
Description: It includes 1. Introduction 2. Nomenclature 3. Preparation of alkynes 4. Reactions of alkynes 5. Practice questions
Description: It includes 1. Introduction 2. Nomenclature 3. Preparation of alkynes 4. Reactions of alkynes 5. Practice questions