• Skip to main content
  • Skip to primary sidebar
  • Skip to footer
  • NCERT Solutions
    • NCERT Books Free Download
  • TS Grewal
    • TS Grewal Class 12 Accountancy Solutions
    • TS Grewal Class 11 Accountancy Solutions
  • CBSE Sample Papers
  • NCERT Exemplar Problems
  • English Grammar
  • MCQ Questions

CBSE Tuts

CBSE Maths notes, CBSE physics notes, CBSE chemistry notes

Characterize the IR spectrum of methyl benzoate?

Characterize the IR spectrum of methyl benzoate?

Answer:
First, let’s get the structure down. Methyl, indicating the alkyl group coming off the bottom-right carboxyl oxygen of a benzyl ester group.
Characterize the IR spectrum of methyl benzoate Img 1
Within this molecule, we have the following relevant bonds:
C=C (aromatic)
C-H (aromatic)
C=O (ester)
C-H (alkanes)

Notice how a double bond will not easily bend, so we don’t really talk about those bending, only stretching.

Within the bonds we’ve just listed, we have the following resonant frequencies that characteristically coincide with the most prominent vibrational activities of each functional group (Techniques in Organic Chemistry; Mohrig, Hammond, and Schatz):

C=C (aromatic)

\(\text { 1620 1440 cm }^{-1}\) medium to weak strength (stretch)

C − H (aromatic)

\(3100 \sim 3000 \mathrm{~cm}^{-1}\) medium to weak strength (stretch)
\(900 \sim 680 \mathrm{~cm}^{-1}\) strong strength (bend)

C=O (ester) — conjugated

\(1730 \sim 1715 \mathrm{~cm}^{-1}\) strong strength (stretch)

C – O (ester)

\(1300 \sim 1000 \mathrm{~cm}^{-1}\) strong strength (stretch)

C – H (alkanes)

\(2990 \sim 2850 \mathrm{~cm}^{-1}\) medium to strong strength (stretch)
\(1480 \sim 1430,1395 \sim 1340 \mathrm{~cm}^{-1}\) medium to weak strength (bend)

You can see the spectrum here:
Characterize the IR spectrum of methyl benzoate Img 2
Specifically:

  • The aromatic C=C stretch is the thin weak peak you see near 1600
  • The aromatic C-H bend is the thin strong peak you see near 700 and the stretch is the thin, well-defined, weak peaks right above 3000
  • The ester C=O conjugated stretch is the strong, slightly wide peak right above 1700
  • The ester C-O stretch is the strong, slightly wide peak you see right below 1300
  • The alkane C-H bends are the thin medium/weak peaks you see near 1500~1300 (including the “sidearm” off of the ester peak) while the single thin weak peak near 3000 is the stretch.

BONUS POINTS: can you spot the \(\mathrm{CO}_{2}\) peak in your spectrum? Here’s a hint: it’s near \(2400 \mathrm{~cm}^{-1}\)

Primary Sidebar

NCERT Exemplar problems With Solutions CBSE Previous Year Questions with Solutoins CBSE Sample Papers

Recent Posts

  • MCQ Questions with Answers for Class 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, and 1 all Subjects
  • Angle, Types of Angles
  • AND gate is formed by using two? 1)OR 2)NAND 3)NOT 4)NOR
  • And expression for one minus the quotient of one and a number X?
  • What is average human body temperature in Kelvins?
  • How many moles of caffeine are in a cup, and how many molecules of caffeine?
  • How far will the car have traveled in that time?
  • What is its atomic number?
  • How many neutrons does it have?
  • An atom loses electrons to form what?
  • What is the atomic number of this atom?
  • Which one of these is the answer?
  • What is its concentration?
  • Can an equilateral triangle also be isosceles?
  • What is the charge of an alpha particle?

Footer

Maths NCERT Solutions

NCERT Solutions for Class 12 Maths
NCERT Solutions for Class 11 Maths
NCERT Solutions for Class 10 Maths
NCERT Solutions for Class 9 Maths
NCERT Solutions for Class 8 Maths
NCERT Solutions for Class 7 Maths
NCERT Solutions for Class 6 Maths

SCIENCE NCERT SOLUTIONS

NCERT Solutions for Class 12 Physics
NCERT Solutions for Class 12 Chemistry
NCERT Solutions for Class 11 Physics
NCERT Solutions for Class 11 Chemistry
NCERT Solutions for Class 10 Science
NCERT Solutions for Class 9 Science
NCERT Solutions for Class 7 Science
MCQ Questions NCERT Solutions
CBSE Sample Papers
cbse ncert
NCERT Exemplar Solutions LCM and GCF Calculator
TS Grewal Accountancy Class 12 Solutions
TS Grewal Accountancy Class 11 Solutions