CHEM219 / CHEM 219 Module 5 Exam Questions
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Q: Generic formula for alcohols
Answer
R-OH
Q: phenol
Answer
hydroxy-substituted aromatic molecules (any compound with an -OH attached to a benzene
ring)
Q: IUPAC system rules for naming organic alcohols
Answer - organic alcohols are named by replacing the suffix of the parent chain of the molecule with
the suffix -ol
- The parent chain is numbered so as to give the hydroxyl group the lowest possible
number. (examples: 1-propanol, and cyclohexanol)
- with unsaturated alcohols the -ol suffix comes last and takes priority when numbering the
parent chain (2-propene-1-ol)
- Molecules with more than one -OH group get a prefix describing the number of -OH
groups added to the IUPAC name. (ethane-1,2-diol)
Molecules with more than one -OH group
polyols
Q: IUPAC rules for phenols
Answer - the suffix for an alcohol substituted benzene is "phenol" - start the numbering at the OH group (so OH is at the 1 position)
(examples: phenol, 3-methylphenol, 2,4-dinitrophenol)
Q: Why can alcohols form strong hydrogen bonds?
Answer
These attractions raise the amount of energy required to vaporize the liquid-phase
molecules (boil), which translates into increased boiling point temperatures.
Due to the presence of the hydroxyl group, as the O-H bond is highly polarized by the
electronegative oxygen atom. This polarization places a + charge on the hydrogen atom and
a - charge on the oxygen atom. The polarization in the O-H bond on one alcohol molecule
becomes attracted to the polarization in the O-H bond of another alcohol molecule.
Q: Why do alcohols have much higher boiling points than other molecules of similar
molecular weight?
Answer
hydrogen bonding between alcohol molecules
Q: Alcohol molecules can freely hydrogen bond to other molecules possessing what
groups?
Answer
O-H, N-H, or S-H functional groupings
Q: How does the water solubility of alcohol molecules change as the molecular weight
changes?
Answer
Alcohol molecules of lower molecular weight are mostly soluble in water as a result of the
ability to hydrogen bond to OH, NH, or SH groups. As the molecular weight or carbon
chain length increases, the alcohol molecules become correspondingly less soluble in water.
Q: How do alcohols and phenols act as weak acids and weak bases?
Answer - acts as an acid by donating the O-H proton as H - acts as a base by accepting H+ using a lone pair on the O atom
Q: amphoteric substances
Answer
Substances that can act as both acids and bases (alcohols and phenols)
Q: Why is acid dissociation for most alcohols unfavorable (lies towards the left)?
Answer
Dissociation produces an alkoxide ion (the conjugate base of an alcohol), which is a very
strong base.
Q: How can you conduct acid-base reactions that favor the formation of weaker conjugate
acids/bases?
Answer
To promote (favor) the formation of the alkoxide ion, the alcohol can be treated with
sodium or potassium metal (Na or K) or a base that is stronger than the RO- ion produced.
Q: protonation of an alcohol
Answer - A specific type of elimination reaction. In a dehydration reaction, an alcohol molecule will
lose H2O to form an alkene. Alcohols undergo a reaction known as dehydration when they
When alcohols act as weak bases by using a lone pair on the oxygen atom of the hydroxyl
group, alcohols can accept a proton when they are placed in an acidic environment.
Q: What is the product of the protonation of an alcohol called?
Answer
alkyloxonium ion
What is a Dehydration reaction for alcohols?
Q: What happens during a dehydration reaction for alcohols?
Answer
are heated with strong mineral acids (like sulfuric or phosphoric).
- the alcohol molecule loses the hydroxyl (OH) from one carbon (the α-carbon) and a
hydrogen atom (H) from an adjacent (β) carbon.
Q: What is the function of an acid during a dehydration reactions? Why does it do what it
does?
Answer
To protonate the the OH group
It does this to make it a better (more stable) leaving group because H2O is a neutral while
hydroxide ion is strongly basic.
Q: What type of mechanism is a dehydration reaction for a sterically bulky tertiary
alcohol?
Answer
E1 mechanism
Q: Steps of a dehydration reaction for a tertiary alcohol
Answer - the OH group is pronated (the alcohol acts as a base and accepts a proton from the acid
solvent onto its OH group) - the OH group disassociates, forming a carbocation - then water, acting as a base, removes a β-hydrogen to form the alkene.
- The net result is that H and OH are removed (eliminated) from the original alcohol
substrate. - products: an alkene and H3O+
Q: What type of mechanism is a dehydration reaction for a sterically non-bulky primary
alcohol?
Answer
E2 mechanism
Q: Why do primary alcohols dehydrate through the E2 mechanism?
Answer
Because these substrates do not form stable carbocation intermediates.
Q: Steps of a dehydration reaction for a primary alcohol
Answer - hydroxyl (OH) group is pronated by the solvent - a water molecule (from the solvent?) removes a β-hydrogen. - As the β-hydrogen is
removed the bond H-C bond is broken and then there is a C=C bond formed between the β
carbon and the α-carbon. - At the same time. the double bond kicks off the H2O molecule from the α-carbon
- The net result is that H and OH are removed (eliminated) from the original alcohol
substrate. - products: an alkene and H3O+
Q: What is the order of ease of dehydration of alcohol substrates?
Answer
3° > 2° > 1°
Tertiary alcohols require the least harsh reaction conditions (typically 25% aqueous acid
and 60-80°C), whereas 1° alcohols require fully concentrated acid and temperatures
approaching 200°C.
Q: When can a single alcohol substrate produce more than one alkene product?
Answer
This occurs when a β-hydrogen can be removed from different carbons to create the C=C in
different places on the parent chain.
Q: Zaitsev's Rule
Answer
In cases where more than one alkene product is possible, the major product is always the
alkene whose C=C has more alkyl groups attached. The greater the substitution (the
number of alkyl groups) attached to the C=C, the more stable the alkene.
Q: What type of reaction is it when alcohols are converted to alkyl halides?
Answer
A substitution reaction
Replacing the hydroxyl group with a halogen
Q: What are the different halides that can be used for Alcohols -> Alkyl Halides
Conversion?
Answer - Conversion using Hydrogen Halides (HX) - Conversion using Phosphorus Halides (PX3) - Conversion using Thionyl Chloride (SOCl2)
Q: What are the two ways the use of hydrogen halides promotes substitution?
Answer
1. The acid protonates the hydroxyl group of the alcohol to make it a good leaving group.
2. The halide ions are good nucleophiles but weak bases, so substitution is promoted over
elimination.
What is the order of ease for reactivity of alcohols with hydrogen halides?
Primary alcohols react much more slowly and require much more harsh reaction
conditions. For example, the conversion of 1-butanol to 1-chlorobutane requires the use of
Q: What conditions do the reactions of different alcohol structures require?
Answer
Tertiary > Secondary > Primary alcohols
Tertiary alcohols react the fastest under the mildest conditions. Example: The reaction of 2
methyl-2-propanol with HCl. This reaction occurs by an SN1 mechanism (tertiary
substrate) and can be performed at room temperature (R.T.) in as little as fifteen minutes.
Secondary alcohols react at intermediate rates by either SN1 or SN2 mechanisms,
depending on the structure of the specific alcohol.
concentrated hydrochloric acid and a catalyst (typically zinc chloride) and strong heating
for several hours to accomplish the same conversion. Primary alcohols react via an SN2
mechanism.
How can the reaction of a primary alcohol converting into an alkyl halide via SN2
mechanism by influenced by a ZnCl2 solvent?
Answer
Primary alcohols react via an SN2 mechanism. The hydroxyl group of the alcohol is
protonated and then displaced as a water molecule by a chloride ion.
Zinc chloride can serve a similar role as that of a proton by accepting a lone pair from the
hydroxyl oxygen atom. Zinc chloride also can dissociate to provide more chloride ions into
the reaction mixture, thus increasing the concentration of the nucleophile and the rate of
the overall reaction.
With a Phosphorus trihalide reagent (PX3), which halides can be X?
Answer
Cl or Br
This reaction is particularly efficient as one molecule of PX3 can convert three molecules of
alcohol to the corresponding alkyl halide.
Which alcohol structures can be converted to alkyl chlorides and bromides using
Phosphorus trihalide reagents?
Answer
Primary and Secondary structures
What is the stoichiometric benefit of Conversion using Phosphorus Halides (PX3)?
Answer
What is a byproduct of the conversion via phosphorus halides? Why is it beneficial for
distillation?
Answer
A byproduct of the reaction is phosphorus acid (H3PO3), which has a rather high boiling
point. This makes isolation of the (relatively) low boiling alkyl halide product easy by
distillation.
What is the molecular formula for the reagent thionyl chloride?
Answer
SOCL2
What does using Thionyl Chloride (SOCl2) for conversion of alcohols produce? Which type
of structures can this conversion using SOCl2 be used on?
Answer - used to convert alcohols to the corresponding alkyl chloride.
- very efficient for primary and secondary alcohols.
What is the advantage of using Conversion via Thionyl Chloride?
Answer
Although there is no stoichiometric advantage in this reaction (like with PX3), the
advantage to this reaction is that the main byproduct (SO2) is formed as a gas and leaves
the reaction mixture.
Oxidation
Answer
Oxidation is recognized in organic molecules by increasing the oxygen content (the number
of oxygen atoms) or the oxygen character (more bonds to oxygen).
What kind of alcohol structures can go through oxidation?
primary and secondary alcohols
What are the products of oxidation of alcohols?
Carbonyl containing compounds: Aldehydes, Ketones, Carboxylic Acids
How does the oxidation of primary alcohols differ from the oxidation of secondary alcohols?
Primary alcohols are initially oxidized to aldehydes, which can then be oxidized further to
carboxylic acids.
Secondary alcohols are oxidized to ketones. No further oxidation (outside of combustion,
which destroys the molecule) is possible.
This is added to a solution of the alcohol dissolved in acetone as the solvent. Chromic acid is
a strong oxidizing agent and will oxidize primary alcohols to carboxylic acids without
stopping at the aldehyde stage. Secondary alcohols are oxidized to ketones.
There are various chemical reagents that can accomplish the oxidation of alcohols to
carbonyl compounds. What are some chemical reagents for oxidation?
chromic acid (H2CrO4)
potassium permanganate (KMnO4)
sodium hypochlorite (NaOCl)
Jones' Reagent - what is it? What are its disadvantages?
The mixture of chromium trioxide (CrO3) with aqueous sulfuric acid. Produces chromic
acid (H2CrO4).
One obvious disadvantage of using Jones' Reagent is that it is a strong oxidizer and will not
permit the synthesis of aldehydes from primary alcohols.
What benefit is PCC (pyridinium chlorochromate) for oxidation reactions?
PCC will accomplish the oxidation for a primary alcohol to the aldehyde stage and stop
there without further oxidation to the carboxylic acid.
A disadvantage of using Jones' Reagent is that it is a strong oxidizer and will not permit the
synthesis of aldehydes from primary alcohols (it will continue to the carboxylic acid stage).
For this purpose, a mild oxidizing reagent known as PCC is used.
How do tertiary alcohols react during oxidation reactions?
Tertiary alcohols are unreactive in these types of oxidation reactions. Research into the
mechanism of these types of oxidations has revealed that the alcohol must have at least one
hydrogen attached to the carbon on the hydroxyl-bearing carbon.
ethers
All ethers are organic molecules in which two alkyl or aryl (R) groups are covalently bonded
to a single oxygen atom. The generic formula for an ether is R-O R'. The R groups can be the
same (symmetric ether) or they can be different (asymmetric ether).
Nomenclature of Ethers and Epoxides
Go to Module 5.3
alkoxy substituent
an -OR group attached to the parent chain
methoxy
The name for a substituent attached to the parent chain of just O-CH3
Epoxides
Three-membered cyclic ethers, composed of two carbon atoms and a single oxygen.
Epoxides are also known as oxiranes. The small, three-membered ring of an epoxide is very
highly strained (severe angle strain), and as a result, epoxides are useful in synthesis where
atoms or groups can be added to the epoxide molecule using a ring-opening reaction.
crown ethers
Macrocyclic (large ring) polymeric ethers are known as crown ethers because their rings
have a distinct repeating pattern that resembles a crown.
Nomenclature for crown ethers
The naming conventions for crown ethers follow the pattern "[x]crown-y", where "x" is a
number that reflects the ring size, and "y" represents the number of oxygen atoms. The
oxygen atoms are usually separated from one another by two carbon atoms.
What is the special ability of crown ethers?
Crown ethers are a special class of ethers, as they have the ability to solvate cations (+)
within the interior cavity of their ring structures. The lone pairs of the oxygen atoms in the
ring can bind to cationic species and hold them. The size of the ring controls which cations
can fit into the cavity.
This phenomenon is important because it allows ionic compounds to be dissolved in
relatively non-polar organic solvents.
Why do ethers have lower boiling points than that of an alcohol of the same molecular
weight?
Due to their atomic connectivity, ethers do not have any O-H covalent bonds and, thus, are
incapable of forming hydrogen bonds with one another. The lack of intermolecular
attraction causes ethers to boil at much lower temperatures than their constitutionally
isomeric alcohols.
The boiling point of an ether is very similar to a hydrocarbon of corresponding molecular
weight
What type of hydrogen bonds can ethers do?
Although ethers cannot form hydrogen bonding attractions with molecules of each other,
the lone pairs of electrons on the oxygen of an ether can form hydrogen bonds to molecules
that have O-H, N-H, or S-H bonds as a part of their structure. In other words, ethers cannot
donate hydrogen bonds but can accept them from other molecules. Ethers can accept
hydrogen bonds from alcohols, and water.
What happens to the water solubility of an ether as the size of the R groups of an ether
increases?
As the size of the R groups of an ether increases, the water solubility of the ether decreases
as the hydrocarbon portion of the molecule overwhelms the ability of the molecule to make
hydrogen bonds.
Describe ethers as solvents
Ethers are relatively inert compounds. For this reason, they are often used as solvents for
reactions or to prepare solutions containing relatively reactive materials. Most organic
compounds dissolve in ethers.
Ethers as extraction solvents
Used to isolate/collect organic compounds from their natural sources. The low boiling point
of ethers makes them easy to remove from an extract.
Volatility of ethers
Ethers, in general, are volatile (low boiling point). This volatility presents a danger as well -
most small ethers are highly flammable and should not be used in a location where sources
of open flame are found (such as Bunsen or Fisher burners). Electrically operated heat
sources or steam are used to heat ether-based (ethereal) solutions. Long-term exposure to
oxygen in air can cause the formation of explosive peroxides in ethers.
Why is the dehydration of alcohols to produce ethers limited to the synthesis of symmetric
ethers from primary alcohols?
If the desired ether is asymmetric, or the complexity of the R groups increases, the overall
yield of the desired ether product is reduced.
With the goal of forming more complex ethers (especially asymmetric ethers), what is one
mode of preparation available but not the most preferred option?
addition of alcohols to alkenes
During this reaction an alcohol is used as the solvent instead of water and acts as the
nucleophile, resulting in the overall addition of H (from the acid catalyst) and -OR (from
the alcohol) across the double bond of the alkene, breaking the double bond and forming a
more complex/asymmetrical ether.
With the goal of forming asymmetric ethers, what mode of preparation preferred? What are
the steps?
Williamson Synthesis
This method uses two steps to produce an asymmetric ether.
1. In the first step, an alcohol is converted to its conjugate base (alkoxide ion, RO-) usually
by reacting the alcohol with sodium or potassium metal.
2. The alkoxide is then reacted as a nucleophile in an SN2 displacement, typically on an
alkyl halide substrate.
The net result of the two reactions is the formation of an ether where R does not = R'.
What is necessary about the R and R' groups of a Williamson Synthesis in order for their to
be a higher yield of product?
The R' group would need to have a smaller steric bulk (primary or secondary), which would
allow for the SN2 mechanism in the second step. If the R' group is sterically bulkier than
the R group, it would have to go through an E2 mechanism which would have a smaller
yield of product.
what does "unhindered" mean?
Less sterically bulky (primary or secondary strucutres)
Although mostly inert, ethers can be forced to react under very specific reaction conditions
(typically harsh/extreme conditions). The typical mode of reaction of an ether is .....?
Cleavage
What is the cleavage reaction of an ether?
What type of molecule is used to perform the cleavage?
Breaking apart of the ether by severing a C-O bond of the ether by an HX.
Typically, ethers react with strong acids and heat to undergo cleavage.
If the alkyl groups of the ether are unhindered, what mechanism will be used to sever the C
O bond?
The C-O bond can be broken by reaction with a halogen nucleophile in an SN2 reaction
after protonation of the ether oxygen
What happens during a cleavage reaction if the alkyl groups are unhindered?
The halogen bonds to the less-hindered R group (creating the alkyl halide), and the
oxonium ion is displaced to form an alcohol (containing the larger, more-hindered R
group).
What happens during a cleavage reaction if the alkyl groups are hindered (tertiary)?
If the alkyl groups are bulky/sterically hindered (tertiary), the ether typically cleaves by an
SN1 mechanism, as these groups can form the stable carbocation intermediate that defines
the SN1 mechanism. In this case, the ether oxygen atom remains with the less-hindered
alkyl group and the halide bonds to the more-hindered alkyl group.
What are the initial products of the cleavage of an ether using HX? What happens is excess
HX is present?
The initial products of the cleavage of an ether using HX are one equivalent of alcohol and
one equivalent of alkyl halide.
If excess HX is present, the alcohol formed via cleavage may react to form another
equivalent of alkyl halide. Cleavage reactions can be used to help determine the structure of
complex, naturally occurring ethers because the products of the cleavage reaction are
smaller and more easily analyzed fragments. Working backward from the fragments, the
structure of the original ether can be deduced.
What is a peroxyacid (or peracid) and what is it used for?
A peroxyacid is analogous in structure to a carboxylic acid but contains an extra oxygen
between the carbonyl and hydroxyl group.
A reagent used to synthesis epoxides from alkenes.
What happens during a epoxidation reaction?
An alkene reacts with a peroxyacid to form an epoxide.
- an oxygen is transferred from the peroxyacid to the alkene - the C=C p bond is broken and incorporates the oxygen atom as part of a three-membered
ring.
Why are epoxides more reactive than ethers?
Due to the significant amount of ring strain in epoxides, they are much more reactive than
regular ethers and undergo reactions through opening of the three-membered ring.
What is a common way to open the three membered ring of a epoxides?
Treat the molecule with aqueous acid (a mixture of acid and water).
What happens during a reaction between epoxides and aqueous acid or alcohols? What is
the product? - initial protonation of the epoxide oxygen - followed by a nucleophilic attack of water on one of the epoxide carbons - SN2 where the leaving group remains attached to the other carbon atom of the original
epoxide ring
The product of an acid-catalyzed ring opening of an epoxide is a diol, specifically a vicinal
diol (two hydroxyl groups on adjacent carbons).
vicinal diol
two hydroxyl groups on adjacent carbons
Alcohol
Generic formula R-OH, defined by the presence of a Hydroxyl group (-OH). Organic
derivatives of water, as one of the hydrogen atoms from the water molecule is replaced by
an alkyl group.
Phenols
Hydroxyl group directly attached to a benzene ring
Methyl Alcohol
Only H atoms attached to the carbon bearing the-OH group
Primary Alcohol
one alkyl group attached to the carbon atom bonded to the -OH group
Secondary Alcohol
Two alkyl groups attached to the carbon atom bonded to the -OH group
Tertiary Alcohol
Three alkyl groups attached to the carbon atom bonded to the -OH group
Boiling Point of Alcohols
High due to Hydrogen bonding between the positively charged H and negatively charged O
Alkoxide Ion
conjugate base of an alcohol, very strong base
Water solubility of alcohols
As the carbon chain length increases alcohol becomes correspondingly less soluble in water.
Alcohols Acidity/Basicity
Can act as a weak base (accepting H+ using a lone pair on the O atom) or weak acid
(donating the O-H proton as H+)
Amphoteric
a substance that can act as both an acid and a base
Alkyloxonium Ion
The conjugate acid of the alcohol is often called a protonated alcohol,
Dehydration
Loss of water. An alcohol molecule will lose H2O to form an ALKENE. Type of elimination
reaction — lose the -OH from one C and H atom from the adjacent C.
First step — alcohol acts as a base.
Tertiary alcohols - E1
Primary alcohols - E2
All dehydration begins with...
Protonation of the alcohol group.
Order of ease of dehydration of alcohol substrates...
3>2>1
Tertiary require the least harsh conditions (typically 25% aqueous acid and 60-80 degrees
C) whereas primary require fully concentrated acid and temperatures approaching 200
degrees C.
If more than one alkene product is possible...
The major product is the one whose C=C has more alkyl groups attached.
ZAitsev's Rule
The production of the more highly substituted alkene as the major product.
Alcohols —> Alkyl Halides -Substitution REaction , replacing the -OH with a halogen -Alcohol (R-OH) + Hydrogen Halide (H-X) ——> alkyl halide (R-X) + water (H-OH)
-the use of Hydrogen halides promotes the substitution in two ways
1. Acid protonates the -OH of the alcohol to make it a good leaving group
2. Halide ions are good nucleophiles but weak bases so substitution is promoted over
elimination
Order of Reactivity of Alcohols with HX
3>2>1
Primary Alcohols react via.... (With HX)
Sn2 -OH group is protonated and then displaced as a water molecule by a chloride ion
Secondary Alcohols react via... (with HX)
Sn1 or Sn2 - depending on the structure of the specific alcohol
Conversion using Phosphorous Halides (PX3)
X= Cl or Br - Alcohol (3R-OH) + phosphorous trihalide (X2P-X) —> alkyl halide (3R-X) + H3PO3 -particularly efficient as one molecule of PX3 can convert 3 molecules of alcohol to the
corresponding alkyl halide -byproduct of the reaction is phosphorous acid
Conversion using Thionyl Chloride (SOCl2)
Alcohol (R-OH) + Thionyl Chloride (Cl-S=O-Cl) —> alkyl Chloride (R-Cl) + SO2 ^ + HCl - very efficient with primary and secondary alcohols d/t the main byproduct (SO2) beig
formed as a gas and leaving the reaction mixture.
Oxidation to Aldehydes, Ketones and CArboxylic Acids
Oxidation - increasing the oxygen content (number of oxygen atoms) or the oxygen
character (more bonds to oxygen) -Primary Alcohols —> aldehydes —> Carboxylic Acids -SEcondary Alcohols —>ketones -Tertiary - unreactive
Jones Reagent
Cromium Triioxide with aqueous sulfuric acid —> Chromic Acid
Disadvantage - strong oxidizer and wil not permit the synthesis of aldehydes from primary
alcohols
Oxidizing agents that convert alcohols to Carbonyl compounds
Potassium Permanganate (KMnO4)
Sodium Hypochlorite (NaOCl)
PCC Oxidation of Alcohols
Pyridinium Chlorochromate - oxidizes primary alcohols to the aldehyde stage and stop
there without further oxidation to the Carboxylic acid. -Dichloromethane (CH2Cl2) is typically the solvent used for PCC oxidation o alcohols
Ether
Alkyl or Aryl group that are covalently bonded to a single O atom.
Generic Formula : R-O-R' (R groups can be the same - symmetric or different - asymmetric)
Epoxides
Three-member Ed cyclic ethers - composed of two C atoms and a single O atom.
Also known as Oxiranes.
Very highly strained (severe angle strain)
Useful in synthesis where atoms or groups can be added to the Epoxide molecule using a
ring-opening reaction
Macrocyclic
Large ring polymer ethers
Crown ethers - because their rings have a distinct repeating pattern
[X]crown-y ; X= ring size ; y= number of oxygen atoms
Crown Ethers
Can solvate cations within theur interior cavity, size of the ring controls which cations can
fit into the cavity, this allows ionic compounds to be dissolved in relatively non-polar
organic solvents
Properties of Ethers
Clear, Colorless, with characteristic odors
Lower BP than alcohols with similar molecular weights
Cannot H bond
Boiling point is similar to a hydrocarbon of corresponding molecular weight
Can not form H bonds to each other, but can form H bonds to O-H, N-H or S-H to the lone
pair of O
As the R groups increase, water solubility decreases
Ethers as Solvents
Relatively inert
Make excellent extraction solvents (used to isolate/collect organic compunds from theur
natural sources)
Low boiling point
Highly flammable
Preparation by Addition of Alcohols to Alkenes
Williamson Synthesis
Two steps to produce an asymmetric ether, in fist step alcohol is converted to its conjugate
base, (Alkoxide ion RO-) by reacting the alcohol with sodium or potassium metal. The
Alkoxide is then reacted as a nucleophile in an Sn2 displacement, typically on an alkyl
halide substrate. Net result is an ether where R does not equal R. Typically primary or
secondary only.
Cleavage by HX
Typical mode of reaction is cleavage (breaking apart of the ether by severing a C-O bond of
the ether. Usually react with strong acids and heat.
Tertiary - Sn1; ether O remains with the less-hindered alkyl group and the halid bonds to
the more hindered alkyl group.
Initial products of cleavage of an ether are an alcohol and an alkyl halide.
Synthesis of expoxides from alkenes
Use peracid (peroxyacid). Forms by transfer of the extra O to the alkene. C=C bond is
broken and incorporates the O atom as a part of a 3 membered ring.
Peroxyacid
Analogous in structure to a Carboxylic acid but contains an extra oxygen between the
carbonyl and hydroxy group
Reactions of Expoxides with waters and alcohols
Epoxides are much more reactive due to their ring strain.
A common way to open the ring is to treat it with aqueous acid.
Sn2 - initial protonation of the expoxide O , followed by nucleophilic attack of water on one
of the epoxide Carbons.
Vicinal Diol
Product of an acid-catalyzed ring opening of an epoxide.
Two hydroxyl groups on adjacent carbons.
Aldehydes
Presence of a carbonyl group (C=O) with at least one H attached to the carbonyl C and the
remaining valence may be another H atom or an alkyl or aryl group.
Ketones
Presence of a carbonyl group (C=O), carbonyl C is directly connected to two other C based
groups.
IUPAC aldehyde nomenclature -al (suffix)
Parent chain is named based in the number of C in the longest chain containing H
C=O(formal group)
IUPAC ketone nomenclature -one suffix
Parent chain is the longest contiguous chain that contains the Carbonyl group, numbering
begins at the end of the chain nearest the carbonyl carbon
Nucleophilic Addition
Attack of the nucleophile at the positive carbonyl carbon, this attack is typically followed by
addition of a proton (hydrogen) to the carbonyl oxygen
Dipole-dipole attractions
Cause the molecules to associate with the + part of one molecule attracted to the - part of
another.
Stronger than van der walls forces, but weaker than H bonding.
Aldehydes are reduced to...
Primary alcohols
Ketones are reduced to...
Secondary alcohols
Hydride transfer reducing agents
Most widely used reagent to reduce aldehydes and ketones. They reduce aldehydes and
ketones by producing hydride ion (H:-) in solution. Hydride ion is a potent nucleophile and
can react with the carbonyl C of an aldehyde or ketone.
Ex. Sodium Borohydride (NaBH4)
Sodium Borohydride (NaBH4)
Advantages - reduces all aldehydes and ketones. Stable and can be used in mixed aqueous
systems. Very efficient as one Borohydride can transfer all 4 of its H atoms as hydride ions
and reduce 4 carbonyls
The difference between most additions of aldehydes and ketones is WHEN the proton gets
bonded to the carbonyl carbon...
Acidic environment - proton bonds to carbonyl O before the nucleophile attacks which
makes the C=O more reactive towards nucleophilic attack and is useful when a weaker
(uncharged) nucleophile is used.
Basic Environment - the strong (typically negative) nucleophile attacks first, followed by
subsequent protonation of the Alkoxide oxygen.
Nomenclature of Carboxylic Acids -oic acid
Numbering begins with carboxyl carbon atom
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