ORGANIC CHEMISTRY ACS LATEST 2025
REAL EXAM QUESTIONS AND CORRECT
ANSWERS ALREADY GRADED A+ JUST
RELEASED.
⫸ What is off-resonance decoupled spectra? Answer: Removes all the info
about the hbumber of hydrogens attached to each carbon; removes someof
the coupling of carbons to hydrogens so that the coupled peaks will not
overlap
⫸ What does mass spec measure? Answer: Produces a spectrum of masses
based on the structure of a molecule; a mass spectrum is a plot of the
distribution of ion masses corresponding to the formula weight of a
molecule and/or fragments derived from it;
- x axis represents the masses of ions produced
- y axis represents the relative abundance of each ion produced
- use fragmentation to impart the ions
-fragments are sorted accroding to their masses to charge ratio (m/z)
- most of the fragements detected have charge +1; the net effect is sorting
of the ions by mass (m/z)
- alkyl substitued benzenes often lose a hydrogen or alkyl group to yield the
relatively stable tropylium ion
- other substitued benzenes usually lose their substituents to yield a phenyl
cation
⫸ Alcohols usually show a M+ 18 peak from. Answer: loss of water
⫸ Carbonyl compounds can undergo a mclafferty rearrangement. Answer:
,⫸ How are radicals formed? Answer: Homolytic bond cleavage --> radicals
are highly reactive and short lived
- relatively weak bonds such as O-O, X-X can occur with the addition of
energy in the form of heat or light
ex. dialkyl peroxide --> alkoxyl radicals
⫸ What is hydrogen abstraction? Answer: halogen radical can react to pair
with its unshared electron
(alkane --> alkyl radical R)
⫸ Homolytic bon dissociation energies. Answer: Atoms have higher energy
(less stable) than the molecules they can form; the formation of covalent
bonds is exothermic
- breaking covalent bonds requires energy (endothermic)
- homolytic bond dissociation is DH = positive)
⫸ Radical stability ranking. Answer: Tertiary > secondary > primary >
methyl
⫸ How do alkanes react with halogens? Answer: alkanes undergo
substitution reactions iwth halogens such as fluorine, bromine, and
chlorine in the presence of heat or light ; forms hydrogen halide
⫸ How can we radically halogenate all hydrogen atoms? Answer: Just use
halogens (usually most if not all will react) - but the some of the number of
moles of each halogenated methane produced equals the number of moles
of methane that reacted).\
- methane +x2 --> heat or light --> tetrahalomethane
,⫸ How can we control the amount of radically halogenated compounds
that form. Answer: Use a large excess of methane - to make a
monohalogenated produced and an excess of unreacted methane (large
excess of alkane :) )
methane + x2 --> heat or light --> halomethane
⫸ Chlorine as a halogenating reagent. Answer: -Chlorine is relatively
unselective and doesn't greately distinguish between type of hydrogen -->
leads to monochlorinated product (and more substituted product)
+polychlorinated products +hcl
⫸ What are the steps of radical reactions? Answer:
⫸ What is the most endothermic-demanding process of the radical
reaction? Answer: chain initiation
⫸ What is the order of reactivity in methane substitution with halogens?
Answer: fluorine > chlorine > bromine > iodine
⫸ Can you explain why fluorine and iodine are not used in radical
formation? Answer: Fluorination has a low value for Eact for the first step
and is extremely exothermic therefore fluorination reactions are explosive
Chlorination and bromination ahve increasinlgly higher values of Energy of
activation and lower delta H values which makes these halogenation
reactions less vigorous
Iodonination has a prohibitively high value for Eact of the first step and the
reaction does not occur
⫸ Halogens are deacitvaitng but have both. Answer: inductive electron
, withdrawing and resonance donating (electronegativity and lone pair
donation)
⫸ What is the aldol condensation reaction? Answer: reaction in which an enol
or an enolate ion reacts with a carbonyl compound to form a beta
hydroxyaldehyde or b-hydroxyketone, followed by dehydration to give a
conjugated enone.
⫸ How does one transform a fischer projection into a cyclic ring in chair
conformation? Answer: Freely rotate the bonds (change the position of the OH
and CH2OH in the fischer projection, then the oyxgen-H bond will
nucleophilically attack the carbon, kick the double bond of the oxygen to the
oxygen to form an oxygen anion and then get protonated by a hydrogen from
the alcohol gorup used to nucleophilically attack the carbon. (mechanism is in
notebook)
⫸ What reaction uses BuLi? Answer: Correy Fuches
⫸ What is the starting and end product of the Ph3P, Br- ? Answer: ketone;
alkene
⫸ What is LiAlh4? Answer: A reducing agent; carboxylic acid and ester can be
reduced by this in addtiiton to aldehydes or ketones
⫸ What happens in a free-radical additon of H-Br to alkenes? (HBr RO-OR).
Answer: antiadditon or syn addition of H and Br. Antimarkovnikov.
⫸ Enolate (ester) --> ketone. Answer: NaOEt --> PhCh2Br --> H3O+, heat
(Remove CO2)
REAL EXAM QUESTIONS AND CORRECT
ANSWERS ALREADY GRADED A+ JUST
RELEASED.
⫸ What is off-resonance decoupled spectra? Answer: Removes all the info
about the hbumber of hydrogens attached to each carbon; removes someof
the coupling of carbons to hydrogens so that the coupled peaks will not
overlap
⫸ What does mass spec measure? Answer: Produces a spectrum of masses
based on the structure of a molecule; a mass spectrum is a plot of the
distribution of ion masses corresponding to the formula weight of a
molecule and/or fragments derived from it;
- x axis represents the masses of ions produced
- y axis represents the relative abundance of each ion produced
- use fragmentation to impart the ions
-fragments are sorted accroding to their masses to charge ratio (m/z)
- most of the fragements detected have charge +1; the net effect is sorting
of the ions by mass (m/z)
- alkyl substitued benzenes often lose a hydrogen or alkyl group to yield the
relatively stable tropylium ion
- other substitued benzenes usually lose their substituents to yield a phenyl
cation
⫸ Alcohols usually show a M+ 18 peak from. Answer: loss of water
⫸ Carbonyl compounds can undergo a mclafferty rearrangement. Answer:
,⫸ How are radicals formed? Answer: Homolytic bond cleavage --> radicals
are highly reactive and short lived
- relatively weak bonds such as O-O, X-X can occur with the addition of
energy in the form of heat or light
ex. dialkyl peroxide --> alkoxyl radicals
⫸ What is hydrogen abstraction? Answer: halogen radical can react to pair
with its unshared electron
(alkane --> alkyl radical R)
⫸ Homolytic bon dissociation energies. Answer: Atoms have higher energy
(less stable) than the molecules they can form; the formation of covalent
bonds is exothermic
- breaking covalent bonds requires energy (endothermic)
- homolytic bond dissociation is DH = positive)
⫸ Radical stability ranking. Answer: Tertiary > secondary > primary >
methyl
⫸ How do alkanes react with halogens? Answer: alkanes undergo
substitution reactions iwth halogens such as fluorine, bromine, and
chlorine in the presence of heat or light ; forms hydrogen halide
⫸ How can we radically halogenate all hydrogen atoms? Answer: Just use
halogens (usually most if not all will react) - but the some of the number of
moles of each halogenated methane produced equals the number of moles
of methane that reacted).\
- methane +x2 --> heat or light --> tetrahalomethane
,⫸ How can we control the amount of radically halogenated compounds
that form. Answer: Use a large excess of methane - to make a
monohalogenated produced and an excess of unreacted methane (large
excess of alkane :) )
methane + x2 --> heat or light --> halomethane
⫸ Chlorine as a halogenating reagent. Answer: -Chlorine is relatively
unselective and doesn't greately distinguish between type of hydrogen -->
leads to monochlorinated product (and more substituted product)
+polychlorinated products +hcl
⫸ What are the steps of radical reactions? Answer:
⫸ What is the most endothermic-demanding process of the radical
reaction? Answer: chain initiation
⫸ What is the order of reactivity in methane substitution with halogens?
Answer: fluorine > chlorine > bromine > iodine
⫸ Can you explain why fluorine and iodine are not used in radical
formation? Answer: Fluorination has a low value for Eact for the first step
and is extremely exothermic therefore fluorination reactions are explosive
Chlorination and bromination ahve increasinlgly higher values of Energy of
activation and lower delta H values which makes these halogenation
reactions less vigorous
Iodonination has a prohibitively high value for Eact of the first step and the
reaction does not occur
⫸ Halogens are deacitvaitng but have both. Answer: inductive electron
, withdrawing and resonance donating (electronegativity and lone pair
donation)
⫸ What is the aldol condensation reaction? Answer: reaction in which an enol
or an enolate ion reacts with a carbonyl compound to form a beta
hydroxyaldehyde or b-hydroxyketone, followed by dehydration to give a
conjugated enone.
⫸ How does one transform a fischer projection into a cyclic ring in chair
conformation? Answer: Freely rotate the bonds (change the position of the OH
and CH2OH in the fischer projection, then the oyxgen-H bond will
nucleophilically attack the carbon, kick the double bond of the oxygen to the
oxygen to form an oxygen anion and then get protonated by a hydrogen from
the alcohol gorup used to nucleophilically attack the carbon. (mechanism is in
notebook)
⫸ What reaction uses BuLi? Answer: Correy Fuches
⫸ What is the starting and end product of the Ph3P, Br- ? Answer: ketone;
alkene
⫸ What is LiAlh4? Answer: A reducing agent; carboxylic acid and ester can be
reduced by this in addtiiton to aldehydes or ketones
⫸ What happens in a free-radical additon of H-Br to alkenes? (HBr RO-OR).
Answer: antiadditon or syn addition of H and Br. Antimarkovnikov.
⫸ Enolate (ester) --> ketone. Answer: NaOEt --> PhCh2Br --> H3O+, heat
(Remove CO2)
