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Functional Groups


Functional Groups aldehyde Definition: an organic compound containing a Carbonyl group ( C=O ). The aldehyde group is generaly written -CHO the name Aldehyde comes ... – PowerPoint PPT presentation

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Title: Functional Groups

Functional Groups
(No Transcript)
  • Definition an organic compound containing a
    Carbonyl group ( CO ).

The aldehyde group is generaly written -CHO
  • the name Aldehyde comes from Alcohol-dehydrogenate
    d meaning the loss of hydrogen

Benzaldehyde aroma in cherries, almonds, perfumes
Carboxyl Group
  • Definition a Carboxyl group ( -COOH), double
    bonded to an oxygen and single-bonded to the
    oxygen of the hydroxyl group
  • Polar, water-soluble
  • The H dissociates and thus has acidic
    properties. Compounds with this functional group
    are called carboxylic acids

The Carboxyl group is generally written -COOH
Carboxylic acids are the most important acids of
organic chemistry. They are present or in derived
form in many natural substances Amino acids
(building blocks of proteins). Note that the
amino acids also contain an amine group. Below
is given the structure of alanine Fatty acids
(building blocks of lipids) are long aliphatic
chains terminated by the carboxyl group. The
structure of stearine is given below.
Fatty acid
Glutamic acid
Carbonyl Group
  • Definition functional group consisting of a
    carbon atom double-bonded to oxygen
  • (-CO)
  • Polar, involved in H-bonding and molecules with
    this functional group are water-soluble
  • Found in sugars
  • If the carbonyl is at the end off the carbon
    skeleton-the compound is an aldehyde
  • If the carbonyl is at the end of the carbon
    skeleton, the compound is a ketone

  • Definition an alcohol is an organic compound
    containing a hydroxyl group ( O-H ). The molecule
    on the left (methanol) shows the alcohol
    functional group

OH-CH2-CH2-OH ethylene glycol (antifreeze)
Definition an Amine is a derivative of ammonia (
NH3 ) in which hydrogen atoms are replaced by R
Alanine cysteine
Phosphate group
  • Definition functional group which is the
    dissociated form of phosphoric acid
  • Has acid properties since it loses H (protons)
  • Polar and soluble in water
  • Important in cellular energy storage and transfer

Sulfhydryl group
  • Definition functional group consisting of an
    atom of sulfur bonded to an atom of hydrogen
  • Help stabilize structure of proteins-disulfide
    bridges in the tertiary structure of proteins
  • Called thiols when found in organic compounds

Carbon atoms and molecules of carbon
Methane ethane
Single, double, triple bonds
Isomers have the same molecular formula but
different structures and different properties

Structural isomers

These two chlorine atoms are locked on opposite
sides of the double bond. This is known as the
trans isomer the two chlorine atoms are locked on
the same side of the double bond. This is know as
the cis isomer. (Hint if you build models and
have to take it apart-geometric isomer)
free rotation about single bonds these two
structures represent the same molecule (Hint if
you build model-you just have to rotate c-c bond-
not an isomer)
Cis/trans geometric isomers
  • In triglycerides fatty acids may contain double
    bonds, which can be in either the cis or trans
    configuration .
  • Fats with at least one double bond between carbon
    atoms are unsaturated fats. When some of these
    bonds are in the cis configuration, the molecules
    cannot pack tightly, so they remain liquid (oil)
    at room temperature.
  • triglycerides with trans double bonds (called
    trans fats), have are linear fatty acids that are
    able to pack tightly together at room temperature
    and form solid fats.

  • Whenever a carbon atom has four different
    structures bonded to it, two different molecules
    can be formed. (chiral means the central C is
    bonded to 4 different groups or atoms)
  • EXAMPLE the amino acid alanine. Bonded to its
    alpha carbon atom are
  • a carboxyl group (COO-)
  • an amino group (NH3)
  • a methyl group (CH3)(its R group)
  • a hydrogen atom
  • If you orient the molecule so that you look along
    it from the COO- group to the NH3 group, the
    methyl (R) group can extend out
  • to the left, forming L-alanine (shown below on
    the left) or
  • to the right, forming D-alanine (on the right).

  • Although they share the same chemical formula,
    they are not interchangeable any more than a
    left-hand glove is interchangeable with
    right-hand glove.
  • 19 of the 20 amino acids used to synthesize
    proteins can exist as L- or D- enantiomorphs. The
    exception is glycine, which has two
    (indistinguishable) hydrogen atoms attached to
    its alpha carbon.
  • L amino acids are used exclusively for protein
    synthesis by all life on our planet. (Some D
    amino acids are used for other purposes.)

  • The function of a protein is determined by its
  • A protein with a D amino acid instead of L will
    have its R group sticking out in the wrong
  • Many other kinds of organic molecules exist as
    enantiomers. Usually only one form is active in
    biological systems. For example, if one form
    binds to a receptor protein on the surface of a
    cell, the other probably cannot.
  • Cells usually synthesize only one form. However,
    chemical synthesis in the laboratory or
    pharmaceutical factory usually produces equal
    amounts of the two enantiomers called a racemic
  • Example The drug albuterol (e.g., Proventil)
    contains equal amounts of two enantiomers. Only
    one of them is effective, and the other may be
    responsible for the occasional unpleasant
    side-effects associated with the drug (which is
    used to dilate the bronchi, e.g, during an attack
    of asthma).

Chiral compounds
  • Some chemical compounds have optical activity in
    the sense that these compounds have the ability
    to rotate the plane of polarized light. Polarized
    light has light waves all traveling parallel to
    each other. Ordinary light has light waves
    traveling in all directions. When polarized light
    is passed through a solution of an optically
    active compound, the plane of polarization is
    rotated to the right or the left. The angle of
    rotation can be measured in a polarimeter.
  • An optically active organic compound can be
    identified by finding a chiral carbon. A chiral
    carbon is one that has four different "groups"
    attached to it. The groups can be anything from a
    single H to functional groups to one or more
    other carbons. See bromochloroiodomethane on the
    left - it has 3 halogens and one hydrogen.
  • In relatively complicated compounds, each carbon
    must be examined carefully to determine whether
    it is chiral. Some compounds may have two or more
    chiral carbon centers such as in carbohydrates.
  • See glyceraldehyde Carbon 1 has only three
    groups attached. Carbon 3 has two hydrogens
    which count as 2 of the same groups. Finally,
    carbon 2 has four different groups attached.