“functional groups”. functional groups l most organic chemistry involves substituents –often...
TRANSCRIPT
“Functional Groups”
Functional GroupsMost organic chemistry involves
substituents–often contain O, N, S, or P–also called “functional groups”- they
are the chemically functional part of the molecule, and are the non-hydrocarbon part
Functional Groups Functional group - a specific
arrangement of atoms in an organic compound, that is capable of characteristic chemical reactions.–What is the best way to classify
organic compounds? By their functional groups.
Functional GroupsThe symbol “R” is used to
represent any carbon chains or rings
- alkyl groups
Halogen Substituents
Halocarbons - class of organic compounds containing covalently bonded fluorine, chlorine, bromine, or iodine
– General formula: R-X (X = halogen) Naming? Name parent as normal, add the
halogen as a substituent (or prefix) -
Halogen Substituents
The more highly halogenated the compound is, the higher the b.p.
Few halocarbons found in nature
–but, readily prepared and used
–halothane and also the hydrofluorocarbons
Substitution Reactions
Organic reactions often much slowerslower than inorganic reactions– must break strong covalent bond– trying to find new catalysts to use
Substitution - an atom (or group of atoms) replaces another atom or group of atoms
Substitution Reactions
A halogen (shown as “X”) can replace a hydrogen to make a halocarbon:
R-H + X2 R-X + HX Sunlight is often a sufficient catalyst:
CH4 + Cl2 → CH3Cl + HClUV light
Substitution ReactionsTreating benzene with a halogen?
Halogens on carbon chains are readily displaced by hydroxide ions (OH1-) to make an alcohol + a salt:
R-X + OH1- R-OH + X1-
CH3-Cl + NaOH CH3-OH + NaCl
Methanol + sodium chloride
Substitution Reactions
CH3-I + KOH CH3-OH + KI
CH3CH2Br + NaOH CH3CH2OH + NaBr
Iodomethane Methanol
Bromoethane Ethanol
Alcohols and Ethers
Alcohols Alcohols - a class of organic compounds with
an -OH group– The -OH functional group in alcohols is
called a “hydroxyl” group; thus R-OH is the formula
How is this different from the hydroxide ion? (covalent bonding with the carbon- not ionic with a metal like bases)
Alcohols Aliphatic alcohols classified into
categories according to the number of R groups attached to the carbon with the hydroxyl–1 R group: primary alcohol–2 R groups: secondary alcohol–3 R groups: tertiary alcohol
Alcohols Both IUPAC and common names For IUPAC:
–drop the -e ending of the parent alkane name; add ending of -ol, number the position of -OH
–parent is the longest chain that contains the carbon with the hydroxyl attached.
AlcoholsThe hydroxyl is given the
lowest position numberAlcohols containing 2, 3, and 4
of the -OH substituents are named diols, triols, and tetrols respectively
AlcoholsCommon names:
–similar to halocarbons, meaning name the alkyl group, then followed by the word alcohol
–One carbon alcohol = methyl alcohol
Alcohols More than one -OH substituents
are called glycols (ethylene glycol?) Phenols - compounds in which a
hydroxyl group is attached directly to an aromatic ring. Cresol is the common name of o, m, and p isomers of methylphenol
Properties of Alcohols
Much like water, alcohols are capable of hydrogen bonding between molecules
–this means they will boil at a higher temp. than alkanes and halocarbons with a comparable number of atoms
Properties of Alcohols Alcohols are derivates of water; the
-OH comes from water, and thus are somewhat soluble
Alcohols of up to 4 carbons are soluble in water in all proportions; more than 4 carbons are usually less soluble, because the longer carbon chain is more nonpolar
Properties of Alcohols Many aliphatic alcohols used in
laboratories, clinics, and industry
–Isopropyl alcohol (2-propanol) is rubbing alcohol; used as antiseptic, and a base for perfume, creams, lotions, and other cosmetics
Ethylene glycol (1,2-ethanediol) - commonly sold as “antifreeze”
Properties of AlcoholsGlycerol (1,2,3-propanetriol) -
used as a moistening agent in cosmetics, foods, and drugs; also a component of fats and oils
Ethyl alcohol (ethanol) used in the intoxicating beverages; also an important industrial solvent
Properties of AlcoholsDenatured alcohol- means it
has been made poisonous by the addition of other chemicals, often methyl alcohol (methanol, or wood alcohol).
As little as 10 mL of methanol has been known to cause permanent blindness, and 30 ml has resulted in death!
Addition Reactions The carbon-carbon single bond is
not easy to break In double bonded alkenes, it is
easier to break a bond Addition reaction- substance is
added at the double or triple bond location, after it is broken
Addition Reactions Addition of water to an alkene is a
hydration reaction - usually occurs with heat and an acid (such as HCl or H2SO4 acting as a catalyst)
Note the formation of ethanol from ethene + water
Addition Reactions If a halogen is added in an addition
reaction, the result is a halocarbon that is disubstituted –
The addition of bromine is often used as a test for saturation - Addition of a hydrogen halide? -called monosubstituted halocarbon
Addition Reactions Addition of hydrogen to produce an
alkane is a hydrogenation reaction, which usually involves a catalyst such as Pt or Pd
–common application is the manufacture of margarine from unsaturated vegetable oils (making them solid from a liquid)
Addition Reactions
The hydrogenation of a double bond is a reduction reaction, which in one sense is defined as
the “gain of H” ethene is “reduced” to ethane;
cyclohexene is “reduced” to cyclohexane
Ethers A class of organic compounds in
which oxygen is bonded to 2 carbon groups: R-O-R is formula
Naming? The two R groups are alphabetized, and followed by ether
Two R groups the same? Use the prefix di-
Ethers Diethyl ether is the one commonly
called just “ether”
–was the first reliable general anesthetic
–dangerous- highly flammable, also causes nausea
ethers are fairly soluble in water Alcohol used for fuel in the future?
Carbonyl Compounds
Aldehydes and KetonesReview:
–alcohol has an oxygen bonded to a carbon group and a hydrogen
–ether has an oxygen bonded to two carbon groups
An oxygen can also be bonded to a single carbon by a double bond
Aldehydes and Ketones The C=O group is called the
“carbonyl group”
–it is the functional group in both aldehydes and ketones
Aldehydes - carbonyl group always joined to at least one hydrogen (meaning it is always on the end!)
Aldehydes and KetonesKetones - the carbon of the
carbonyl group is joined to two other carbons (meaning it is never on the end)
Aldehydes and Ketones Naming?
–Aldehydes: identify longest chain containing the carbonyl group, then the -e ending replaced by -al, such as methanal, ethanal, etc.
–Ketones: longest chain w/carbonyl, then new ending of -one; number it?
propanone, 2-pentanone, 3-pentanone
Aldehydes and Ketones
Neither can form intermolecular hydrogen bonds, thus a much lower b.p. than corresponding alcohols
wide variety have been isolated from plants and animals; possible fragrant odor or taste; many common names
Aldehydes and KetonesBenzaldehydeCinnamaldehydeVanillinMethanal (the common name is:
formaldehyde)–40% in water is formalin, a
preservative
Aldehydes and KetonesPropanone (common: acetone)
is a good solvent; miscible with water in all proportions
why is it a good substance used in nail-polish removers? (a powerful solvent-able to dissolve both polar & nonpolar)
The Carboxylic Acids… Also have a carbonyl group (C=O),
but is also attached to a hydroxyl group (-OH) = “carboxyl” group
general formula: R-COOH
–weak acids (ionize slightly) Named by replacing -e with -oic
and followed by the word acid methanoic acid; ethanoic acid
Carboxylic Acids Abundant and widely distributed in
nature, many having a Greek or Latin word describing their origin
–acetic acid (ethanoic acid) from acetum, meaning vinegar
–many that were isolated from fats are called fatty acids
The Esters… General formula: RCOOR Derivatives of the carboxylic acids,
in which the -OH from the carboxyl group is replaced by an -OR from an alcohol:
carboxylic acid + alcohol ester + water many esters have pleasant, fruity
odors- banana, pineapple, perfumes
EstersAlthough polar, they do not form
hydrogen bonds (reason: there is no hydrogen bonded to a highly electronegative atom!)
–thus, much lower b.p. than the hydrogen-bonded carboxylic acids they came from
EstersCan be prepared from a
carboxylic acid and an alcohol; usually a trace of mineral acid added as catalyst (because acids are dehydrating agents)
EstersNaming? It has 2 words:
–1st: alkyl attached to single bonded oxygen from alcohol
–2nd: take the acid name, remove the -ic acid, add -ate
Oxidation- Reduction Reactions All of the previous classes of
organic compounds are related by oxidation and reduction reactions
What is oxidation-reduction?
–Oxidation: the gain of oxygen, loss of hydrogen, or loss of e-1
–Reduction: the loss of oxygen, gain of hydrogen, or gain of e-1
Oxidation- Reduction ReactionsOxidation and reduction
reactions (sometimes called redox) are coupled- one does not occur without the other
The number of Oxygen and Hydrogen attached to Carbon indicates the degree of oxidation
Oxidation- Reduction Reactions
The fewer the # of H on a C-C bond, the more oxidized the bond–Thus, a triple bond is more
oxidized than a double bond and a single bond
An alkane is oxidized (loss of H) to an alkene, and then to an alkyne
Oxidation- Reduction Reactions
Loss of hydrogen is called a dehydrogenation reaction
–may require strong heating and a catalyst
Oxidation- Reduction Reactions Methane can be oxidized in steps
to carbon dioxidemethane methanol methanal methanoic acid CO2
the more reduced (more H) a carbon compound, the more energy it can release upon oxidation
Oxidation- Reduction ReactionsAlcohols can also be oxidized
into other products “Dr. Al K. Hall Mr. Al D. Hyde”Preparing aldehydes from a
primary alcohol is a problem, because they are then easily oxidized to carboxylic acids
Oxidation- Reduction Reactions
Benedict’s test and Fehling’s test are commonly used for aldehyde detection –
Polymerization
Addition PolymersPolymers are giant molecules,
not small like the ones studied earlier in this chapter–examples are plastics
Polymer- large molecule formed by the covalent bonding of smaller molecules called monomers
Polymers from Monomers
Addition PolymersAn addition polymer forms when
unsaturated monomers react to form a polymer–ethene will form polyethylene,
–polyethylene is easy to clean, chemically resistant- milk bottles, plastic wrap, refrigerator dishes
High Density Polyethylene
Addition Polymers Polypropylene is a stiffer polymer, used
in utensils and containers Polystyrene is formed from styrene
(phenylethene), and is a poor heat conductor (styrofoam ® Dow Chemical)
–molded coffee cups and picnic coolers, insulates homes
Polyvinyl chloride (PVC) used for pipes in plumbing
Addition PolymersPolytetrafluoroethene (PTFE, or
teflon ® DuPont) is very resistant to heat and chemical corrosion–found on nonstick cookware;
coating on bearings and bushings used in chemical reactors
Condensation PolymersCondensation polymers are
formed by the head-to-tail joining of monomer units
–usually accompanied by the loss of water from the reacting monomers, and forming water as a product
Condensation Polymers Ex: polyethylene terephthalate (PET)
–Dacron (® DuPont), Fortrel (® Wellman), Polyesters: permanent press clothing, tire cords
–Sheets of polyester called Mylar (® DuPont), used as magnetic tape in tape recorders and computers, as well as balloons
–Nylon: carpet, fishing line, hosiery
Condensation Polymers Examples:
–aromatic rings form Nomex (® DuPont), which is a poor electrical conductor; makes parts for electrical fixtures; flame resistant clothing for race car drivers; flame resistant building materials
–Kevlar (® DuPont): strong and flame resistant
Plastic container code system.
CODE MATERIALPERCENT OF
TOTAL
Polyethylene Terephthalate
(PET)20-30 percent
High Density Polyethylene 50-60 percent
Polyvinyl Chloride (PVC) 5-10 percent
Low Density Polyethylene 5-10 percent
Polypropylene 5-10 percent
Polystyrene 5-10 percent
All other resins 5-10 percent
What Do the Numbers Mean?1 -- PETE (Polyethylene terephthalate)
•PET (or PETE) is used in the production of soft drink bottles, peanut butter jars... •PET can be recycled into fiberfill for sleeping bags, carpet fibers, rope, pillows...
What Do the Numbers Mean?2 -- HDPE (High-density polyethylene)
•HDPE is found in milk jugs, butter tubs, detergent bottles, motor oil bottles... •HDPE can be recycled into flower pots, trash cans, traffic barrier cones, detergent bottles...
What Do the Numbers Mean?
3 -- V (Polyvinyl chloride)•PVC is used in shampoo bottles, cooking oil bottles, fast food service items... •PVC can be recycled into drainage and irrigation pipes...
What Do the Numbers Mean?
4 -- LDPE (Low-density polyethylene)
•LDPE is found in grocery bags, bread bags, shrink wrap, margarine tub tops... •LDPE can be recycled into new grocery bags...
What Do the Numbers Mean?
5 -- PP (Polypropylene)•PP is used in most yogurt containers, straws, pancake syrup bottles, bottle caps.... •PP can be recycled into plastic lumber, car battery cases, manhole steps...
What Do the Numbers Mean?
6 -- PS (Polystyrene)•PS is found in disposable hot cups, packaging materials (peanuts), and meat trays... •PS can be recycled into plastic lumber, cassette tape boxes, flower pots...
What Do the Numbers Mean?
7 -- Other•This is usually a mixture of various plastics, like squeeze ketchup bottles, "microwaveable" dishes...
Timeline of Plastics1862 – First man-made plastic
1866 – Celluloid makes it’s debut
1891 – Rayon is discovered
1907 – Bakelite is invented
1913 – Cellophane causes the plastics craze
Timeline of Plastics1926 – PVC is invented
1933 – Polyethylene is discovered
1933 – Saran makes it’s debut
1938 – Teflon is discovered
1939 – Nylon stockings hit market
1957 – Here comes velcro