Organic Spectroscopy MCQs [Organic Chemistry]
MCQs-based questions and answers on Organic Spectroscopy in organic chemistry.
A strong signal at 3400 cm-1 in an IR spectrum indicates the presence of a(n)
- Carbonyl
- Amine
- Alcohol
- Alkane
Question’s Answer: Alcohol
Which bonds would be expected to have the highest frequency stretch?
- Carbon-bromine single bond
- Carbon-carbon double bond
- Carbon-carbon triple bond
- Carbon-carbon single bond
Question’s Answer: Carbon-bromine single bond
Which bonds lowest frequency would be expected to have the lowest frequency stretch?
- C-CI
- C-Br
- C-I
- C-F
Question’s Answer: C-I
In UV-Visible spectroscopy, if an auxochrome shifts the position of absorption to longer wavelength there will be
- Hyperchromic effect
- Bathochromic shift
- Hypochromic effect
- Hypsochromic shift
Question’s Answer: Bathochromic shift
The separation of resonance frequencies of protons in different structural environments from some chosen standard is called______.
- Proton resonance
- Chemical exchange
- Spin-spin splitting
- Chemical shift
Question’s Answer: Chemical shift
Which is independent of applied magnetic field in the PMR spectroscopy?
- Spin-spin splitting
- Chemical shift
- Both of these
- None of these
Question’s Answer: Spin-spin splitting
The compound displays the following PMR spectrum only
(i) Triplet for 3 protons (ii) Quartet for 2 protons It is likely to be.
- CH3CH2Br
- CH3CH₂OCH3
- CH3CH2OH
- CH3–O–CH
Question’s Answer: CH3CH2Br
Which arrangement is most stable?
- Triplet state (T₁)
- Single states (S1)
- Singlet state (S2)
- Triplet state (T2)
Question’s Answer: Triplet state (T₁)
Quantum yield for most photochemical reaction is either less or greater than 1 whereas it should have been I according to Einstein law. It is because of
- Primary
- Termination processes
- Secondary processes
- None of these
Question’s Answer: Secondary processes
Benzophenone reacts with isopropyl alcohol in presence of light to form benzopinacol. the reaction is an example of
- Photodimerization
- Photodegradation
- Photoisomezization
- Photoreductionb
Question’s Answer: Photoreduction
Direct irradiation of butadiene along results in the reaction
- Photodimerization
- Photoisomerization
- Photoreduction
- Photooxidation
Question’s Answer: Photodimerization
Photolysis of acetone at room temperature to yield biacetyl and other products is
- Norrish type I reaction
- Norrish type II reaction
- Paterno Buchi reaction
- None of these
Question’s Answer: Norrish type I reaction
Photodimerization of dibenzyl ketone to form dibenzyl and CO is a reaction called______.
- Photodimerization
- Photoisomerization
- Norrish type I reaction
- Norrish type II reaction
Question’s Answer: Norrish type I reaction
Hexane-2-one undergoes photolysis to form propene and acetone. The reaction is an example of
- Norrish type I reaction
- Paterno Buchi reactionc
- Norrish type II reaction
- Photoaddition
Question’s Answer: Norrish type II reaction
Norrish type II reaction involves which of the following?
- Hydrogen abstraction B
- Hydride ion abstraction
- Proton abstraction
- Rearrangement without abstraction
Question’s Answer: Hydrogen abstraction B
Reaction of ketones and alkenes in the presence of light to form oxetanes is known
- Norrish type I reaction
- Paterno Buchi reaction
- Diels-Alder reaction
- Norrish type II reaction
Question’s Answer: Paterno Buchi reaction
Photoirradiation of cyclic α, β-unsaturated ketones result in
- Photoreduction
- Photodimerization
- Photodegradation
- Photoisomerization
Question’s Answer: Photodimerization
Which will absorb at higher wavelength in UV region?
- 1,4-Pentadiene
- 1,3-Pentadiene
- Anthracene
- Naphthalene
Question’s Answer: Anthracene
Which factor will not shift the absorption of ultraviolet radiation to longer wavelength?
- Steric hindrance
- Resonance
- Auxochrome
- Conjugation
Question’s Answer: Steric hindrance
Greatest energy is associated with which radiations?
- Ultraviolet
- X-ray
- Infrared
- Visible
Question’s Answer: X-ray
The electronic transition which required maximum energy is A. σ o
- n → σ
- π → π
- n → π
- σ → σ
Question’s Answer: σ → σ
The value of molar extinction coefficient (∈) is related to
- Wavelength of absorption
- Probability of transition.
- Frequency of absorption
- All of A, B, and C
Question’s Answer: Probability of transition
Bathochromic shift is shifting to
- Lower wave number
- Higher wave number
- Lower wavelength
- None of these
Question’s Answer: Lower wave number
Hypsochromic effect in IR spectrum
- Increases the of absorption
- Lowers the intensity of absorption
- Lowers the wavelength of absorption
- Increase the frequency of absorption
Question’s Answer: Lowers the wavelength of absorption
A chemical reaction that occurs as a consequence of light absorption is called
- Fluorescence
- Photo reduction
- Chemiluminescence
- Photochemical reaction
Question’s Answer: Photochemical reaction
Dissociation of molecule to form free radicals on absorption of light is
- Secondary process
- Primary process
- Fluorescence
- Phosphorescence
Question’s Answer: Primary process
Magnetic properties are not observed in nuclei with
- Odd mass number and odd atomic number
- Even mass number and even atomic number
- Odd mass number and even atomic number
- Even mass number and odd atomic number
Question’s Answer: Even mass number and even atomic number
Which is the nuclei insensitive to nuclear magnetic resonance?
- 16O
- 2H
- 19F
- 1H
Question’s Answer: 16O
What is the spin quantum number (S) for proton?
- 0
- 4
- 1/2
- 3/2
Question’s Answer: 1/2
In vibrational rotational bands, the frequency or wavelength of absorption relies on
- Relative masses of the atoms
- The force constant of the bonds
- Geometry of the atoms
- All
Question’s Answer: All
The relation between wave number (V) and wavelength is given by the expression (where c is the wavelength of light)
- v = c/λ
- v = 1/ λ2
- v = 1/λ
Question’s Answer: v = 1/λ
Vacuum ultraviolet region is __________ .
- 100-200 nm
- 200-400 nm
- 400-800 nm
- 100-400 nm
Question’s Answer: 100-200 nm
Absorption of ultraviolet radiations by a molecule causes which of the following?
- Rotational excitation
- Vibrational excitation
- Electronic excitation
- All of A, B, and C
Question’s Answer: Electronic excitation
Spinning proton can take up how many orientations in an applied magnetic field
- 2
- 1
- 4
- 6
Question’s Answer: 2
Resonance is said to frequency of electromagnetic radiation in a constant magnetic field is equal to _______ spinning nuclei.
- Spinning frequency
- Spin quantum number
- Precessional frequency
- All of A, B, and C
Question’s Answer: Precessional frequency
Total _______ absorption peaks will appear in the PMR spectra of CH3COCH3.
- 1
- 6
- 4
- 2
Question’s Answer: 6
Which statement is true regarding PMR spectra of CH3CHO ?
- Duplet for 3 protons and quartet for 1 proton
- Duplet for 3 protons and singlet for 1 proton
- Singlet for 3 protons duplet for 1 proton
- Quartet for 3 protons and duplet for 1 proton
Question’s Answer: Quartet for 3 protons and duplet for 1 proton
Mass spectrometry studies the spectrum of _____.
- Positively charged ions
- Negatively charged ions.
- Neutral radicals
- All of A, B, and C
Question’s Answer: Positively charged ions
Which is a forbidden transition?
- n-п*
- n-π*
С. π-π*
- None of these
Question’s Answer: n-п*
The parent molecular ion spectrometry is helpful and used to determine in
- Molecular weight
- Bond energy
- Functional group
- All of A, B, and C
Question’s Answer: Molecular weight
Mass spectrum of an alcohol gives a strong peak at m/e 31. The alcohol is likely to be a
- Tertiary alcohol
- Secondary alcohol
- Primary alcohol
- Any one of these
Question’s Answer: Primary alcohol
The parent molecular ion [C6H5COCH3)+ is The parent likely to fragment as
- CH3 + C6H5 – C+ = O
- C6H5 + CH3 – C+ = O
- CH3 + C6H5 – C– = O
- C6H5 + CH3 – C– = O
Question’s Answer: CH3 + C6H5 – C+ = O
The number of rings and double bonds in a positive ion having the formula C7H7
- One ring + 2 double bonds
- Two rings + 1 double bond
- One ring + 3 double bonds
- Two rings + 3 double bonds
Question’s Answer: One ring + 3 double bonds
Which best describes the PMR spectrum of C6H5CHO?
- Two singlet peaks
- One duplet peak + one hexatet peaks
- One duplet + one singlet peaks
- Two duplet peaks
Question’s Answer: One duplet peak + one hexatet peaks
Absorption of radiation by olefins in proper ultraviolet region results in the electronic transition of the type
- σ → σ
- σ → π
С. π → π
- n → π
Question’s Answer: π → π
Excited state formed initially by absorption of radiation by a molecule is usually ___.
- Singlet state
- Triplet state
- Transition state
- None of these
Question’s Answer: Singlet state
The absorption of light by molecules undergoing photochemical reactions usually results in ________ .
- Phosphorescence
- Fluorescence
- Homolytic fission
- Heterolytic fission
Question’s Answer: Homolytic fission
Which electronic transition cannot be studied by quartz ultraviolet spectroscopy?
- n-o*
- п-п*
- 0-0*
- n-n*
Question’s Answer: 0-0*
Which is helpful and used as a source of visible radiation?
- Hydrogen discharge lamp
B: Tungsten filament lamp
- Deuterium discharge lamp
- All of A, B, and C
Question’s Answer: Tungsten filament lamp
Which solvents cannot be helpful and used for the UV/VIS spectral study of aldehydes?
- n-hexane
- Cyclohexane
- Acetronitrite
- Ethanol
Question’s Answer: Ethanol
Which modes of vibrations is in-plane bending?
- Rocking
- Wagging
- Twisting
- None of these
Question’s Answer: Twisting
What is the vibration degree of freedom of molecule of methane?
- Fifteen
- Nine
- Five
- None of these
Question’s Answer: Fifteen
Which bonds show stretching absorption in the 3700-2500 cm¹ region?
- C-C
- C-N
- C-O
- None of these
Question’s Answer: None of these
Which bonds do not show stretching absorption in the 3700-2500 cm-1 region?
- C-H
- C-C
- O-H
- N-H
Question’s Answer: C-C
Which is not helpful and used as a source of IR radiation?
- Nernst filament
- Globar
- Tungsten filament
- None of these
Question’s Answer: Tungsten filament
Which material is helpful and used for making the circular flat plates to hold the sample for IR study?
- Rock salt
- Quartz
- Glass
- All of A, B, and C
Question’s Answer: Rock salt
Which electronic transition occurs when methanol is exposed to ultraviolet radiation?
- n-o*
- п-п*
- n-n*
- None of these
Question’s Answer: n-o*
In which form can a solid sample be studied by IR spectroscopy?
- As a solution
- As a KBr disc
- As a mull
- Any of these
Question’s Answer: Any of these
Which can be helpful and used to prepare the mull of a solid sample for its IR study?
- Toluene
- Benzene
- Nujol
- Water
Question’s Answer: Nujol
Which is commonly helpful and used as a solvent for IR study?
- Methanol
- Ethanol
- Water
- None of these
Question’s Answer: None of these
Which is not commonly helpful and used as a solvent for IR study?
- Carbon disulfide
- Chloroform
- Carbon tetrachloride
- Ethanol
Question’s Answer: Ethanol
Where does the C-H stretching absorption of an olefin appear in an infrared spectrum?
- At 3000 cm-1
- Below 3000 cm-1
- Above 4020 cm-1
- In the 1650-1600 cm-1
Question’s Answer: Above 3000 cm-1
Which compounds does not absorb light in the UV/visible spectrum?
- Aspirin
- Benzene
- Phenol
- All of A, B, and C
Question’s Answer: All of A, B, and C
In infrared spectroscopy which frequency range is called______. the fingerprint region?
- 1400-1200 cm-1
- 600-250 cm-1
- 900-600 cm-1
- 400-900 cm-1
Question’s Answer: 400-900 cm-1
In UV-visible Spectrophotometer, what does absorbance absorption measure?
- The fraction of light of a particular wavelength absorbed by a sample.
- The fraction of light of a particular wavelength transmitted by a sample
- The total amount of light energy absorbed by a sample
- The intensity of light that emerges from a sample
Question’s Answer: The fraction of light of a particular wavelength transmitted by a sample
The main advantage of fluorescence over UV-vis spectroscopy is
- Its compatibility with separation techniques
- Its sensitivity
- That emission spectra give fairy sharp peaks
- Its compatibility with most analytes
Question’s Answer: Its sensitivity
Infrared spectroscopy gives us the important information about _______.
- Molecular weight.
- Melting point.
- Functional groups
- Conjugation.
Question’s Answer: Functional groups
In UV-Visible auxochrome shifts the position of absorption to shorter wavelength there will be
A Hypsochromic shift
- Hyperchromic effect
- Bathochromic shift
- Hypochromic effect
Question’s Answer: Hypsochromic shift
Homodienic components ______ than heterodienic system
- Equally shift the position of absorption to longer wavelength
- Shifts the position of absorption more to the longer wavelength
- Shifts the position of absorption less to the longer wavelength
- None of these
Question’s Answer: Shifts the position of absorption more to the longer wavelength
According to Woodward Fieser rules an increment of ______ is added to parent value for double bond extended conjugation
- 214
- 30
- 15
- 5
Question’s Answer: 30
The IR spectrum of amines show N-H stretching at
- 3050-3550 cm-1
- 1050-3550 cm-1
- 4050-5550 cm-1
- 2050-3550 cm-1
Question’s Answer: 3050-3550 cm-1
The IR spectrum of carboxylic acid show O-H stretching at
- 1250-3550 cm-1
- 1050-3550 cm-1
- 2500-3550 cm-1
- 4050-5550 cm-1
Question’s Answer: 2500-3550 cm-1
The IR spectrum of carboxylic acid show >C-O stretching at
- 2050-3550 cm-1
- 1700-1750 cm-1
- 3000-5000 cm-1
- 1050-3550 cm-1
Question’s Answer: 1700-1750 cm-1
PMR spectra of ethyl acetate is essentially
- Three singlet peaks
- One triplet, one duplet and one singlet peaks
- Two triplet and one singlet peaks
- One quartet, one triplet and one singlet peaks
Question’s Answer: One quartet, one triplet and one singlet peaks
In H-NMR circulating pi-electrons of benzene add to
- Deshielding effect
- Shielding effect
- Both of these
- None of these
Question’s Answer: Deshielding effect
In H-NMR high acetylene adds to electron density in
- Deshielding effect
- Shielding effect
- Both of these
- None of these
Question’s Answer: Shielding effect
In evaluating chemical shift value, the nucleus that is deshieled will have
- May have lower or higher value
- Lower chemical shift value
- Higher chemical shift value
- None of these
Question’s Answer: Higher chemical shift value
Woodward Fieser rules are applied for
- α, β, Unsaturated carbonyl compounds
- Cyclic Hydrocarbons
- Allenes
- Non conjugated polymer
Question’s Answer: α, β, Unsaturated carbonyl compounds
Homoannular diene λmax value according to Woodward Fieser rules
- 214
- 234
- 217
- None of them
Question’s Answer: None of them
Which is true regarding Auxochrome?
- Ph-
- OH, NH2, -OR
- Ethene & Ethyne
- All of A, B, and C
Question’s Answer: OH, NH2, -OR
Which part of spectrophotometer is helpful and used to convert electromagnetic radiation in to monochromatic radiation
- Deuterium lamp
- Monochromator
- Detector
- None of A, B, and C
Question’s Answer: Monochromator
Scissoring, rocking, wagging are the vibration
- Stretching vibration
- Symmetrical vibration
- Bending vibration
- Both a & b
Question’s Answer: Bending vibration
Aromatics have diagnostic peaks in the ________ region of IR spectra
- 1200-1000 cm-1
- 900-700 cm-1
- 1700-1500 cm-1
- None of A, B, and C
Question’s Answer: 900-700 cm-1
Carbonyl displays absorption peaks in IR spectra
- 1900-1600 cm-1
- 1200-1000 cm-1
- Both a & b
- 2300-2100 cm-1
Question’s Answer: 1900-1600 cm-1
Monochromator helpful and used in UV spectroscopy ________
- Laser
- Glass prism
- Grating
- Glass print
Question’s Answer: Grating
The IR spectrum of aldehydes and ketones show strong>C-O stretching at
- 2050-3550 cm-1
- 2050-4000 cm-¹
- 4050-5550 cm-1
- 1700-1750 cm-1
Question’s Answer: 1700-1750 cm-1
The IR spectrum of phenol show O-H stretching at
- 2050-3550 cm-1
- 1050-3550 cm-1
- 4050-5550 cm-1
- 3200-3550 cm-1
Question’s Answer: 3200-3550 cm-1
The IR spectrum of alcohol show O-H stretching at
- 3580-3650 cm-1b
- 1050-3550 cm-1
- 5000-5550 cm-1
- 2050-3550 cm-1
Question’s Answer: 3580-3650 cm-1
Atomic spectra is an example of
- Continuous spectra-
- Line spectra
- Band spectra
- Both A and B
Question’s Answer: Line spectra
Modern method for separation of isotopes
- X-ray
- Chromatography
- Ionization
- Laser separation
Question’s Answer: Laser separation
In new spectrometers each ion hits a
- Ionizer
- Detector
- Collector
- Graph
Question’s Answer: Detector
Force constant gives an idea about the
- Dipole moment of bond
- Reduced mass
- Strength of bond
- Wave number of absorptions
Question’s Answer: Strength of bond
For a linear molecule the number of vibrational degrees of freedom are (where n = number of atoms)
- 3n-5
- 3n-6
- 3n
- Relies on type of atoms
Question’s Answer: 3n-5
Which pair of compounds cannot be distinguished on the basin of UV spectra?
- Ethyl format and methyl acetate
- Benzene and naphthalene
- 1,3-Pentadiene and 1,4-Pentadiene
- Acetaldehyde and benzaldehyde
Question’s Answer: Ethyl format and methyl acetate
Which is not an auxochrome group?
- NHR-
B.-NH2
- -NR
- -NO2
Question’s Answer: -NO2
Mass spectrometer to determine isotopes in solid state is
- Bohr’s
- dempester’s
- Aston’s
- Alison’s
Question’s Answer: dempester’s
In accelerating chamber of spectrometer potential difference is
- 600-7000
- 500-2000
- 300-8000
- 700-9000
Question’s Answer: 500-2000
Far infrared region of the electromagnetic radiation usually lies between
- 1-20 μm
- 100-400 μm
- 50-1000 μm
- 50-200 μm
Question’s Answer: 50-200 μm
Microwave region of electromagnetic spectrum usually lies between
- 500-1000 cm
- 50-100 cm
- 0.1-100 cm
- 60-150 cm
Question’s Answer: 0.1-100 cm
Radio waves region of the spectrum usually lies between
- 100-500 m
- 300-700 m
- 1-1000 m
- 1-100 m
Question’s Answer: 1-100 m
For a particular molecular species, this of the following terms is function of concentration
- Transmission
- Percent transmission
- Absorbance
- All
Question’s Answer: All
Photomultipliers are very sensitive and rapid in their response and are helpful and used as
- Monochromator
- Detector
- Amplifier
- All
Question’s Answer: Detector
The most widely helpful and used flame in atomic absorption is
- Air-coal gas
- Air-propane
- Oxyacetylene
- Air-acetylene
Question’s Answer: Air-acetylene
Which devices is most commonly helpful and used for the formation of an atomic vapor in atomic absorption?
- Sputtering devices
- Electric atomization
- Flame atomization
- Ovens
Question’s Answer: Sputtering devices
Which molecules show rotational spectra?
- CH3CI
- CO
- HCI
- All
Question’s Answer: All
Which statements are true?
- NO, CO, HCl and CHCl3 are infrared active
- CO2, H2O, CH4 and C2H4 are infrared active
- Both are true
- None is true
Question’s Answer: Both are true
Which involve a change in bond angle with reference to a set of co- ordinates arbitrarily set up within the molecule
- Rocking
- Torsional vibration
- Twisting
- All
Question’s Answer: All
Which the following statements are true
- In a non-linear molecule, 3 degrees of freedom describe rotation and there describe transition1 Molecule of
- N atoms has 3N degrees of
- In non-linear molecule 3N-6 degrees of freedom are vibrational degrees of describes transition freedom
- All are true
Question’s Answer: All are true
Which electronic transition occurs when ethane is exposed to ultraviolet radiation?
- n-n*
- σ-σ*
- n-σ*
- n-n*
Question’s Answer: σ-σ*
In order to excite the spectra of many metals in flame photometry which of the B. Nitrogen following is are good oxidants
- Nitrous oxide
- Nitrogen
- Oxygen
- All
Question’s Answer: All
The best flame temperature for an analysis is determined empirically and relies an upon.
- Excitation energy of the element
- How it is combined in the sample
- Presence of other elements
- The sensitivity required
Question’s Answer: The sensitivity required
Which process may occur in flames?
- Ionization
- Excitation
- Translational, vibrational and rotational motions
- Dissociation
Question’s Answer: Ionization
Heteronulear diene has Amax value according to Woodward Fieser rules
- 217
- 214
- 234
- None of them
Question’s Answer: 214
According to Woodward Fieser rules an increment of ____ is added to parent value for exocyclic double bond
A 214
- 30
- 5
- 15
Question’s Answer: 5
According to Woodward Fieser rules an increment of ________ is added to parent value for alkyl substituent or ring residue
- 5
- 30
- 15
- 214
Question’s Answer: 5
In which region of the electromagnetic spectrum does oxygen absorb?
- 400-800 nm
- 200-400 nm
- 10-200 nm
- None of these
Question’s Answer: 10-200 nm
Which electronic transition occurs when acetone is exposed to visible radiation?
- п-n*
- n-n*
- n-o*
- None of these
Question’s Answer: None of these
Absorbed wavelengths in atomic absorption spectrum appear as
- Dark background
- Light lines
- Light background
- Dark lines
Question’s Answer: Dark lines
Lines which appear in absorption and emission spectrum are
- Very different
- Different
- Same
- Far apart
Question’s Answer: Same
Background in atomic absorption spectrum
- Brown
- Dark
- Bright
- Purple
Question’s Answer: Bright
What is the wavelength range of ordinary infrared region?
- 1.8-2.7μm
- 4.0-8.0μm
- 16-1000μm
- 2.5-16μm
Question’s Answer: 2.5-16μm
The position of an infrared absorption band is commonly express by
- Wavelength
- Nanometer
- Wave number
- None of these
Question’s Answer: Wave number
Which modes of vibrations is different from the other?
- Bending
- Stretching
- Deformation
- All of A, B, and C
Question’s Answer: Stretching
Instrument use to collect ions is
- Spectrometer
- Ionizer
- Electrometer
- None
Question’s Answer: Electrometer
Near ultraviolet region of the electromagnetic spectrum usually lies between
- 10-200 nm
- 300-500 nm
- 400-750 nm
- 200-400 nm
Question’s Answer: 200-400 nm
Far ultraviolet or vacuum ultraviolet region usually lies between
- 200-400 nm
- 10-200 nm
- 400-750 nm
- 300-500 nm
Question’s Answer: 10-200 nm
Which are classified as heat detectors?
- Bolometer
- Thermister
- Thermocouplec
- All
Question’s Answer: All
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