Infrared spectrum: interpret all absorptions from the 4000-1400 cm-1 region of the spectrum. Indicate which absorptions come from the ester and which from impurities. Submit the spectrum with your report.
Basics in Organic Reactions Mechanisms
In organic chemistry, the mechanism of an organic reaction is defined as a complete step-by-step explanation of how a reaction of organic compounds happens. A completely detailed mechanism would relate the first structure of the reactants with the last structure of the products and would represent changes in structure and energy all through the reaction step.
Heterolytic Bond Breaking
Heterolytic bond breaking is also known as heterolysis or heterolytic fission or ionic fission. It is defined as breaking of a covalent bond between two different atoms in which one atom gains both of the shared pair of electrons. The atom that gains both electrons is more electronegative than the other atom in covalent bond. The energy needed for heterolytic fission is called as heterolytic bond dissociation energy.
Polar Aprotic Solvent
Solvents that are chemically polar in nature and are not capable of hydrogen bonding (implying that a hydrogen atom directly linked with an electronegative atom is not found) are referred to as polar aprotic solvents. Some commonly used polar aprotic solvents are acetone, DMF, acetonitrile, DMSO, etc.
Oxygen Nucleophiles
Oxygen being an electron rich species with a lone pair electron, can act as a good nucleophile. Typically, oxygen nucleophiles can be found in these compounds- water, hydroxides and alcohols.
Carbon Nucleophiles
We are aware that carbon belongs to group IV and hence does not possess any lone pair of electrons. Implying that neutral carbon is not a nucleophile then how is carbon going to be nucleophilic? The answer to this is that when a carbon atom is attached to a metal (can be seen in the case of organometallic compounds), the metal atom develops a partial positive charge and carbon develops a partial negative charge, hence making carbon nucleophilic.
![Correlation Table for Infrared Spectroscopy
Frequency of Intensity/Shape
absorption
(cm-1)
3650-3590
3600-3200
3400-2400
3500-3300
3340-3270
3100-3000
2960-2850
Strong/sharp
2850-2810 and Medium/ sharp
2750-2700
2260-2220
2260-2100
Medium to strong/
sharp
Weak to medium/
sharp
Strong/sharp
Strong/sharp
Strong/sharp
Strong/sharp
1730-1680* Strong/sharp
1800 and 1750
1810-1760
1750-1730
1740-1680
1720-1680
1700-1630
Strong/sharp
Strong/broad
Strong/ very broad
Medium to strong/
sharp
Strong/sharp
1680-1620
Weak to medium
1600-1450
Strong/sharp
Strong/sharp
Bond/Class of
Compounds
O-H/ alcohols, phenols
O-H/ alcohols, phenols
O-H/ carboxylic acids
N-H/ 1° and 2° amines
and amides
C(sp)-H/ terminal
alkynes
C(sp²)-H/alkenes,
aromatic compounds
C(sp³)-H/ alkanes
C-H/ aldehydes
C=N/nitriles
C=C/ alkynes
C=0/anhydrides
C=0/ acid chlorides
C=0/esters
C=0/ aldehydes
C=0/ ketones
C=0/amides
Additional Comments
Weak to medium/
C=C/ alkenes
sharp
Variable intensity/ C=C aromatic
sharp
Free (not hydrogen bonded)
OH group
Hydrogen bonded OH group
Dimers of carboxylic acids
1° amines and amides give
two absorptions, 2⁰ - one
Usually two absorptions,
one-2820, another -2720
Might not be visible in internal
alkynes
Always two absorptions
Aliphatic: 1740-1720
Aromatic: 1720-1680
C=0/ carboxylic acids Dimer, 1720-1700 aliphatic,
1700-1680 aromatic
Aliphatic: 1730-1700
Aromatic: 1700-1680
1° and 2° amides 1700-1670,
3⁰-1670-1630
1640-1620 if a conjugated
double bond
* Angle strain in the carbonyl group, caused by the size of a small ring, increases the frequency of
the absorption position of the C=0 bond of cyclic ketones; in cyclohexanone the absorption shows
at 1715 cm-¹, in cyclopentanone at 1750 cm-¹, and in cyclobutanone at 1785 cm-¹.](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F4187eb67-fab6-4738-a29b-fa11c290df86%2F0e809536-f6ed-49fb-8685-e978c3209527%2Fqu3zyyi_processed.jpeg&w=3840&q=75)
![100
90
80
70
60
50
40
3500
3000
Orange ester
2018.39
2500
2000
Wavenumber cm-1
1466.25
1500
1000
500](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F4187eb67-fab6-4738-a29b-fa11c290df86%2F0e809536-f6ed-49fb-8685-e978c3209527%2Ftxstyi_processed.jpeg&w=3840&q=75)
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