Esterification: Reflux, Isolation and Purification // HSC Chemistry

00:09:21
https://www.youtube.com/watch?v=SSqVLdd_bEg

概要

TLDRThe video discusses the process of esterification, a chemical reaction between an alcohol and a carboxylic acid that produces an ester and water. It details the steps involved in the reaction, including the use of catalysts such as concentrated sulfuric acid and the importance of heat and reflux to control and enhance the reaction rate. The video explains the setup to avoid risks due to volatility, the role of reflux, and why a heating mantle is preferable over Bunsen burners. The process of isolating the ester with a separating funnel and neutralization using sodium carbonate is demonstrated, followed by purification through distillation. The video also highlights the reversible nature of esterification and touches on hydrolysis, the breaking down of esters in water to revert to alcohol and carboxylic acid.

収穫

  • 🧪 Esterification is a key reaction involving alcohol and carboxylic acid.
  • 🔄 The reaction is reversible, producing esters and water.
  • 🔥 Heat and reflux are used to control the reaction's speed and efficiency.
  • ⚗️ Concentrated sulfuric acid serves as a catalyst in the reaction.
  • ⛔ A heating mantle is safer than a Bunsen burner due to alcohol's flammability.
  • 🧊 Reflux prevents loss and controls temperature to maintain reaction conditions.
  • 🔍 Sodium carbonate aids in isolating the ester by neutralizing acids.
  • 🌡️ Distillation purifies the ester by separation based on boiling points.
  • 👃 A distinct aroma confirms the presence of esters.
  • 💡 Hydrolysis reverses ester formation by adding water.

タイムライン

  • 00:00:00 - 00:09:21

    Esterification is a condensation reaction between an alcohol and a carboxylic acid, producing water as a byproduct. This reversible reaction can re-form the reactants. Esters have structural components derived from both reactants, which allows for the identification of specific alcohols and acids used. For example, propyl propionate comes from propanol and propanoic acid. Ester formation is slow, often requiring heat and a catalyst like concentrated sulfuric acid, which also removes water to shift equilibrium towards ester production. Safety measures like using a heating mantle replace open flames to reduce fire risk. Reflux is applied to maintain reactants and products within the reaction vessel without pressure build-up.

マインドマップ

ビデオQ&A

  • What is esterification?

    Esterification is a condensation reaction between an alcohol and a carboxylic acid, producing an ester and water.

  • Why is sulfuric acid used in esterification?

    Sulfuric acid acts as a catalyst to increase the reaction rate and helps shift the equilibrium to produce more ester.

  • What is the role of reflux in esterification?

    Reflux allows better control of temperature and prevents the loss of volatile compounds, ensuring the reaction continues to completion.

  • How do you isolate the ester in esterification?

    The ester is isolated by using a separating funnel with sodium carbonate to neutralize acids, forming an organic layer containing the ester.

  • Why is a heating mantle used instead of a Bunsen burner?

    A heating mantle is used to avoid fire hazards since alcohols involved in the reaction are flammable.

  • What is a condensation reaction?

    A condensation reaction is a type of organic chemistry reaction where small molecules, usually water, are produced as byproducts.

  • What does the process of distillation do in esterification?

    Distillation purifies the ester by utilizing its lower boiling point, allowing it to be evaporated and condensed separately from other components.

  • What indicates the completion of ester purification?

    The ester can be confirmed by its characteristic aroma, which is notable after purification.

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  • 00:00:05
    esterification
  • 00:00:06
    is a condensation reaction between an
  • 00:00:08
    alcohol functional group and a
  • 00:00:10
    carboxylic acid
  • 00:00:12
    condensation reaction is a type of
  • 00:00:13
    organic chemistry reaction
  • 00:00:15
    that involves the production of a small
  • 00:00:17
    molecule
  • 00:00:19
    usually and in this case water
  • 00:00:21
    esterification is a reversible reaction
  • 00:00:24
    which means the newly formed ester can
  • 00:00:26
    react with water
  • 00:00:28
    to reform the reactants that is the
  • 00:00:30
    carboxylic acid
  • 00:00:31
    and the alcohol in the previous video on
  • 00:00:33
    esters we discussed
  • 00:00:35
    that the structure of an ester consists
  • 00:00:37
    of a carboxylic acid part
  • 00:00:39
    and an alcohol part this information is
  • 00:00:42
    useful
  • 00:00:43
    because we can use it to determine the
  • 00:00:45
    exact carboxylic acid
  • 00:00:47
    and the alcohol that is used to produce
  • 00:00:50
    the ester
  • 00:00:51
    for example the structure of purple
  • 00:00:54
    propanoids
  • 00:00:55
    consists of three carbon atoms in the
  • 00:00:57
    alcohol part
  • 00:00:59
    and three carbon atoms in the carboxylic
  • 00:01:01
    acid part
  • 00:01:03
    this tells us that it is produced from
  • 00:01:05
    propane one oil the alcohol
  • 00:01:07
    and propanoic acid the carbocytic acid
  • 00:01:10
    both of which
  • 00:01:11
    contain three carbon atoms in the
  • 00:01:13
    molecule using the same approach
  • 00:01:15
    butyl ethanoids is formed from butane 1
  • 00:01:18
    0
  • 00:01:19
    and ethanoic acid esterification
  • 00:01:23
    is naturally a very slow reaction so
  • 00:01:26
    usually
  • 00:01:26
    a catalyst and heat are used to increase
  • 00:01:30
    the rate of reaction to produce the
  • 00:01:32
    ester in a shorter amount of time
  • 00:01:34
    concentrated sulfuric acid h2so4
  • 00:01:37
    is the go-to catalyst as it lowers the
  • 00:01:40
    activation energy of the reaction
  • 00:01:42
    by providing an alternate reaction
  • 00:01:44
    pathway heat
  • 00:01:45
    increases the rate of collision between
  • 00:01:47
    molecules and provides
  • 00:01:49
    more energy to the system so more
  • 00:01:52
    molecules have enough energy
  • 00:01:54
    to result in a chemical reaction when
  • 00:01:56
    they collide both effects
  • 00:01:58
    result in a faster reaction besides
  • 00:02:01
    being a catalyst
  • 00:02:02
    concentrated sulfuric acid also provides
  • 00:02:04
    another benefit
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    it has a dehydrating effect so water is
  • 00:02:08
    removed from the reversible reaction
  • 00:02:11
    this causes the equilibrium to shift to
  • 00:02:13
    the
  • 00:02:14
    product side that is the right side of
  • 00:02:16
    the reaction
  • 00:02:17
    to increase the amount of water and this
  • 00:02:19
    is
  • 00:02:20
    according to le chatelier's principle by
  • 00:02:23
    doing so
  • 00:02:24
    the amount of esta produced is further
  • 00:02:27
    increased
  • 00:02:28
    therefore the use of concentrated
  • 00:02:30
    sulfuric acid
  • 00:02:32
    not only increases the reaction rate as
  • 00:02:34
    a catalyst but also
  • 00:02:36
    the ester yield as discussed earlier
  • 00:02:40
    esterification is a condensation
  • 00:02:42
    reaction whereby a water molecule
  • 00:02:44
    is produced along with the ester it is
  • 00:02:47
    important
  • 00:02:48
    to note that the water molecule produced
  • 00:02:50
    consists
  • 00:02:51
    of the oh group from the carboxylic acid
  • 00:02:55
    and the proton from the alcohol molecule
  • 00:02:58
    this also means that the oxygen atom in
  • 00:03:01
    the ester molecule
  • 00:03:02
    always originate from the alcohol when
  • 00:03:05
    performing an
  • 00:03:06
    esterification reaction it is crucial to
  • 00:03:08
    keep in mind
  • 00:03:09
    that the heat should not be supplied by
  • 00:03:12
    a bunsen burner
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    as the naked flame in the present
  • 00:03:15
    alcohol which is a flammable
  • 00:03:17
    substance poses a huge fire hazard
  • 00:03:21
    therefore the bunsen burner is always
  • 00:03:23
    replaced with the heating mantle to
  • 00:03:25
    reduce this risk
  • 00:03:26
    furthermore heating promotes the loss of
  • 00:03:29
    volatile
  • 00:03:30
    compounds that is the alcohol carboxylic
  • 00:03:33
    acid
  • 00:03:34
    and the ester as they evaporate into
  • 00:03:36
    gases this is a problem because we want
  • 00:03:38
    the reactant to remain the vessel
  • 00:03:40
    so they can continue to react to produce
  • 00:03:42
    the ester
  • 00:03:43
    which we also want to preserve as that
  • 00:03:45
    is the goal of the reaction
  • 00:03:48
    to resolve this problem we cannot simply
  • 00:03:51
    place a cap to close the flask as this
  • 00:03:53
    will create another problem
  • 00:03:55
    whereby the pressure builds up in the
  • 00:03:58
    flask
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    which can ultimately lead to the
  • 00:04:01
    breakage of the material
  • 00:04:03
    the solution to these problems is using
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    reflux
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    reflux refers to connecting a long glass
  • 00:04:10
    column
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    to the opening of the flask which allows
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    volatile substances to ascend
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    without building up the pressure in the
  • 00:04:19
    flask
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    to prevent the volatile substances from
  • 00:04:22
    leaving the reaction vessel
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    a condenser is set up around the column
  • 00:04:28
    such that when the cold water flows
  • 00:04:30
    through the condenser
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    it is able to absorb heat from the
  • 00:04:33
    volatile substances in the column
  • 00:04:36
    this causes them to condense and as the
  • 00:04:39
    substances
  • 00:04:40
    return to liquid states they descend
  • 00:04:42
    down the column
  • 00:04:43
    due to gravity the cold water usually
  • 00:04:46
    enters the condenser
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    at the bottom and exits as warm water at
  • 00:04:50
    the top
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    this is so that the flow against gravity
  • 00:04:54
    prolongs the time during which cold
  • 00:04:56
    water can absorb the heat
  • 00:04:58
    and increases the effectiveness of the
  • 00:05:00
    condenser
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    therefore in summary reflux allows for
  • 00:05:04
    faster reaction that is through heating
  • 00:05:07
    without losing volatile substances and
  • 00:05:09
    the pressure inside the flask
  • 00:05:11
    from building up this is a very critical
  • 00:05:14
    reaction condition that we always
  • 00:05:16
    implement when producing esters
  • 00:05:18
    from alcohol and carboxylic acid besides
  • 00:05:22
    heat and reflux acidification is usually
  • 00:05:25
    performed
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    using a round bottom flask which allows
  • 00:05:29
    heat to be absorbed more evenly
  • 00:05:31
    within the reaction mixture boiling
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    chips
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    are used to avoid a phenomenon called
  • 00:05:37
    superheating
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    superheating occurs when the mixture is
  • 00:05:41
    heated above its boiling points
  • 00:05:44
    but no boiling occurs while it may seem
  • 00:05:47
    beneficial for the substances to remain
  • 00:05:49
    in liquid form
  • 00:05:50
    a superheated solution can suddenly boil
  • 00:05:53
    at any time
  • 00:05:54
    causing a violent phenomenon called
  • 00:05:56
    flash boiling
  • 00:05:57
    thus boiling chips are used as a safety
  • 00:06:00
    measure to prevent superheating from
  • 00:06:02
    happening
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    since esterification is a reversible
  • 00:06:05
    reaction the mixture at the end of the
  • 00:06:08
    reaction
  • 00:06:09
    will always be a mixture of ester the
  • 00:06:11
    reactants
  • 00:06:12
    and sulfuric acid to isolate the ester
  • 00:06:16
    we'll be using a separating funnel and
  • 00:06:18
    the help from sodium carbonates
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    when sodium carbonate is added to the
  • 00:06:23
    mixture it neutralizes
  • 00:06:24
    the residual amount of acid that is a
  • 00:06:26
    carboxylic acid and
  • 00:06:28
    sulfuric acid to produce soluble salts
  • 00:06:33
    this is a neutralization reaction when
  • 00:06:35
    the mixture is then transferred into the
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    separating funnel
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    two distinct layers start to form an
  • 00:06:42
    organic layer at the top and a clear
  • 00:06:44
    aqueous layer at the bottom
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    the aqueous layer contains all the
  • 00:06:48
    soluble salts and alcohol
  • 00:06:50
    which is also soluble in water while the
  • 00:06:53
    top organic layer
  • 00:06:54
    contains the ester which is what we want
  • 00:06:57
    to isolate
  • 00:06:58
    the isolation is achieved by discarding
  • 00:07:02
    the bottom aqueous layer through the
  • 00:07:04
    stopcock
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    leaving behind the organic layer this
  • 00:07:08
    process
  • 00:07:09
    is repeated several times until only the
  • 00:07:11
    organic layer remains behind
  • 00:07:13
    in the separating funnel after isolating
  • 00:07:16
    the ester
  • 00:07:17
    it is further purified using
  • 00:07:19
    distillation in our previous video on
  • 00:07:21
    boiling point of esters
  • 00:07:23
    we explained that esters usually have
  • 00:07:25
    lower boiling points
  • 00:07:26
    than alcohol and carbocytic acids
  • 00:07:29
    distillation
  • 00:07:30
    makes use of this boiling point
  • 00:07:32
    difference
  • 00:07:34
    when the temperature of the mixture
  • 00:07:37
    is raised above the boiling point of the
  • 00:07:40
    ester
  • 00:07:41
    the ester evaporates and using a
  • 00:07:43
    condenser it will be further returned
  • 00:07:45
    into liquid states
  • 00:07:46
    and collected in a separate vessel as
  • 00:07:49
    shown here
  • 00:07:50
    if you smell the distillate that is the
  • 00:07:52
    ester you'll recognize
  • 00:07:54
    an aroma and that is the most convenient
  • 00:07:57
    way
  • 00:07:57
    of confirming that the substance is in
  • 00:08:00
    fact an ester
  • 00:08:01
    in summary the production of esters
  • 00:08:04
    consists of three main parts
  • 00:08:06
    the actual formation of the ester by
  • 00:08:09
    reacting an alcohol and carboxylic acid
  • 00:08:12
    in the presence of concentrated sulfuric
  • 00:08:14
    acid
  • 00:08:15
    heat and reflux this is followed by the
  • 00:08:18
    isolation of ester
  • 00:08:19
    using a separating funnel and sodium
  • 00:08:22
    carbonate for neutralization
  • 00:08:24
    when the ester is isolated it is further
  • 00:08:26
    purified using distillation
  • 00:08:28
    whereby the evaporation and subsequent
  • 00:08:32
    condensation of the ester increases the
  • 00:08:34
    purity
  • 00:08:35
    of the final solution the final solution
  • 00:08:38
    can be
  • 00:08:38
    finally identified as an ester by
  • 00:08:41
    smelling
  • 00:08:42
    and identifying the aroma or the scent
  • 00:08:44
    of the product
  • 00:08:46
    while we spent most of the video
  • 00:08:47
    discussing the production of esters
  • 00:08:50
    it is important to remind ourselves that
  • 00:08:52
    this is a reversible
  • 00:08:54
    reaction the reaction between ester and
  • 00:08:56
    water
  • 00:08:57
    produces an alcohol and a carboxylic
  • 00:09:00
    acid
  • 00:09:01
    and this process is referred to as
  • 00:09:03
    hydrolysis
  • 00:09:04
    hydro representing water and lysis
  • 00:09:07
    representing breakdown of the ester
  • 00:09:09
    so using a large amount of water pushes
  • 00:09:13
    the equilibrium
  • 00:09:14
    towards the left side to increase
  • 00:09:16
    concentrations of the carboxylic acid
  • 00:09:18
    and the alcohol
タグ
  • esterification
  • alcohol
  • carboxylic acid
  • chemical reaction
  • sulfuric acid
  • reflux
  • catalyst
  • condensation
  • distillation
  • hydrolysis