Answer to Question #142819 in Organic Chemistry for kithio mshana

Question

amine and amides power point presentation with citation and references
1.Introduction and history (if applicable)2.Classification3.Nomenclature4.Structural Formulas5.Lewis structure of covalent bonding6.Use structural formula to describe reactions such as addition, combustion and polymerization 7.Conclusion

Answer 1

2

Bonding characteristics of nitrogen atoms in

organic compounds

• We saw already that carbon atoms (Group 4A) form
• four bonds to other atoms in organic compounds.
• And oxygen atoms (Group 6A) form two bonds.
• Nitrogen atoms (Group 5A) require three bonds to
• give them octets. Normally, nitrogen atoms are
• involved in three covalent bonds to other atoms.

The important arrangement for this chapter

3

Structure and classification of amines

• Amines are organic derivatives of ammonia (NH3),
• in which one or more alkyl, cycloalkyl, or
• aromatic groups replace hydrogen and bond to the
• nitrogen atom.

4

Structure and classification of amines

• Amines are classified as primary, secondary, and
• tertiary, as we have seen previously for
• alcohols.
• For alcohols, the type of carbon atom (1o, 2o,
• 3o) bound to the OH group determined whether the
• alcohol was primary, secondary, or tertiary.
• For amines, it is the number of carbon groups
• that are bound to the nitrogen atom.

5

Structure and classification of amines

• This is an important difference in the way that
• 1o, 2o, and 3o classification is given.
• The NH2 group of a primary amine can be thought
• of as an amino group. Thus secondary and
• tertiary amines possess substituted amino groups.

6

Structure and classification of amines

7

Nomenclature for amines

• Common and IUPAC systems are used extensively for
• naming amines.
• In the common system, rules similar to what we
• have seen for ethers are employed, naming the
• alkyl/aromatic groups attached to the functional
• group, and then following these with amine

8

Nomenclature for amines

• The IUPAC system for naming amines is as follows
• Select the longest carbon chain bound to the
• nitrogen as the parent chain
• Name the chain by changing the alkane name for
• this chain drop the e and add amine
• Number the chain to give the nitrogen the lowest
• numbering
• The number and identity of other substituents
• (including any on the main chain) are indicated
• at the beginning of the amine name (some are
• attached to N)

9

Structure and classification of amines

• Some examples. First, 1o amines

4-C chain (butane - e amine)

to indicate placement of NH2 group

10

Structure and classification of amines

• For di- and trisubstituted amines, the non-parent
• chains are indicated as N-bonded

11

Structure and classification of amines

• For diamines, the molecule is named as an
• alkane-diamine with NH2 groups numbered.
• And for cases where NH2-substituted alcohols or
• other compound cases are involved, the NH2-group
• is called an amino substituent.

12

Structure and classification of amines

• In cases where substituted parent chains are
• encountered, the substituents are named at the
• beginning of the compounds name

Parent chain pentane Amino-position C-2 of

parent chain CH3- substituents on parent chain

(C-4) and N

13

Structure and classification of amines

• Aromatic amines involve an amine-type nitrogen
• bound to an aromatic ring. The simplest case for
• these is aniline.

14

Structure and classification of amines

• For substituted anilines, the substituent names
• are treated in a manner similar to what was shown
• for substituted parent chain cases

15

Isomerism for amines

• Skeletal and positional isomers for amines are
• possible.
• In skeletal isomers, the carbon chain components
• of the amines differ

16

Isomerism for amines

• Positional isomers differ in the placement of the
• NH2 group along the parent chain.
• Positional isomers are possible for substituted
• amines as well

17

Physical properties of amines

• Amines tend to be gases for low molecular weight
• cases (e.g. up to (CH3)3N, trimethylamine) and
• many heavier ones are liquids at room
• temperature.
• One very noticeable thing about amines is that
• they tend to exhibit strong odors. For example,
• some have a fishy smell

18

Physical properties of amines

• Amine boiling points are intermediate of those
• for alcohols and alkanes of similar molar mass.
• Because of the presence of N-H bond(s) in primary
• and secondary amines, hydrogen-bonding is
• sometimes possible however, because N is not as
• electronegative as O, the N-H bond is not as
• polar as an O-H bond (weaker H-bonding).

19

Physical properties of amines

• Amines tend to be water-soluble because of
• H-bonding interactions with water molecules. In
• fact, amines having fewer than six carbon atoms
• are infinitely water-soluble.
• Water-solubility decreases as
• Chain length increases, and,
• The degree of N-substitution increases

20

Basicity of amines

• Ammonia is one of the few examples of a weak base
• we looked at in the first semester. It reacts
• with water molecules to produce OH- ions, making
• the resulting solution basic
• NH3 H2O D NH4 OH-
• The resulting ion (NH4) is called an ammonium
• ion.
• Amines react with water to produce ammonium-like
• species.
• CH3NH2 H2O D CH3NH3 OH-

ammonium ion

21

Basicity of amines

• A substituted ammonium ion results from the
• reaction between an amine and water.

substituted ammonium ion

Nitrogen tends to bond to three other atoms to

get an octet when it forms four bonds (in an

ammonium salt), the nitrogen structure carries a

positive charge

22

Basicity of amines

• Naming substituted ammonium ions
• Named similar to amine, but with the term
• ammonium ion instead of amine

Methylammonium ion

Methylamine

Others

23

Basicity of amines

• Amines are better bases than oxygen-containing
• compounds.
• A comparison
• Ethers and alcohols have no significant basicity
• in water

A carboxylate ion

(from ethanoic acid)

24

Amine salts

• Amines, because they are basic, can react with
• acids in neutralization reactions. The reaction
• produces an amine salt, as follows
• R-NH2 H-Cl D R-NH3Cl-

amine

amine salt

Naming named as an ammonium chloride

Example (CH3)3NCl- is Trimethylammonium chloride

Amine salts are ionic compounds in which the

positive ion comes from the substituted ammonium

and the negative ion comes from an acid used to

react with the parent amine.

25

Amine salts

• Amine salts are water-soluble many amines
• (having higher molar masses) are not. Thus, in
• order to introduce an amine-based drug into he
• body, it is often converted into the salt form.
• Many pharmaceuticals possess nitrogen centers
• that are protonated to the ammonium form, to make
• them water-soluble, or to stabilize them (they
• are often called hydrochlorides).

Paxil

26

Amine salts

• The neutral form of an amine drug is often called
• its free-base form. In this neutral form, the
• drug may be vaporized (because the intermolecular
• forces that keep it in a condensed state at room
• temperature can be overcome by heating).
• The ionic form has a very high boiling point and
• usually cannot be vaporized without decomposing
• the structure.

27

Preparation of amines and quaternary ammonium

salts

• Preparation of amines from ammonia is possible
• under basic conditions
• NH3 alkyl halide ? 1o amine
• 1o amine alkyl halide ? 2o amine
• 2o amine alkyl halide ? 3o amine
• 3o amine alkyl halide ? quaternary ammonium
• salt

base

base

base

base

28

Preparation of amines and quaternary ammonium

salts

• When ammonia or an amine is treated with an alkyl
• halide in the presence of a strong base, the
• following reaction occurs

alkyl halide

ammonia

substituted amine

29

Preparation of amines and quaternary ammonium

salts

• When this reaction is being carried out, it is
• necessary to remove the amine as it is formed
• before a following alkylation step occurs

30

Heterocyclic amines

• Heterocylic compounds involve ring structures
• that possess non-carbon atoms. We saw some
• examples in earlier chapters (cyclic ethers,
• cyclic esters, etc.)
• Nitrogen heterocycles are frequently encountered
• in biochemistry. Some examples are

31

Heterocyclic amines

• The following nitrogen heterocycles are found
• frequently in biologically relevant structures.
• For example, the purine structure is present in
• caffeine (drug), adenine and guanine (DNA).

32

Heterocyclic amines

• The nitrogen heterocycle shown below is used for
• oxygen transport in the body. The heme structure
• (right) is present in the bloodstream as a
• component of a much bigger molecule (hemoglobin)
• and acquires/releases O2.

33

Selected biologically important amines

• Neurotransmitters substances that are released
• at the end of a nerve which travel across the
• synaptic gap to another nerve and trigger a nerve
• impulse by binding to a chemical receptor site.

34

Selected biologically important amines

35

Selected biologically important amines

• Epinepherine (adrenaline) a central nervous
• system stimulant. Its release causes blood
• glucose levels to rise, blood pressure to
• increase, increased heart rate and muscle
• strength.

36

Selected biologically important amines

• Histamine responsible for the symptoms
• experienced during hay fever. The body stores
• histamines, which are released in the presence of
• pollen/dust/allergens. The response is produced
• when histamines bind to receptor sites in complex
• molecules.
• Antihistamines (present in a medication) bind to
• these same receptor sites, and block the
• histamine response.

37

Alkaloids

• There are some very important nitrogen-containing
• plant extracts (alkaloids) that are used in
• medicinal science (all of which are amines)

38

Structure and classification of amides

• Amides possess a functional group that consists
• of a CO (carbonyl) directly bound to a nitrogen
• The amide functional group involves a nitrogen
• atom (and lone pair), but unlike an amine, the
• nitrogen center is not basic, due to the
• electron-withdrawing effect of the CO group.

39

Structure and classification of amides

• Amides may be primary, secondary, or teritary

40

Structure and classification of amides

• In terms of their structure, amines may be
• aromatic (benzene substituents) for example,
• benzamide
• They may also be cyclic, or even involve multiple
• amide groups in a single ring

A d-lactam

41

Structure and classification of amides

• In Ch-16, we looked at lactones, which were
• cyclic esters
• Lactams are cyclic amides (and heterocycles)

Lactams

42

Nomenclature of amides

• IUPAC system for naming amides
• Like esters, amides are made using carboxylic
• acids. The portion that comes from the
• carboxylic acid is named as a carboxylic acid
• first, before dropping the -oic acid from the
• name and adding -amide
• Substituents attached to the nitrogen are
• prefixed with N- to indicate their position
• other substituents on the parent chain are named
• as part of the parent chain (unlike for amines)

43

Nomenclature of amides

• Some examples
• For aromatic cases

44

Selected amides and their uses

• Urea is one of the simplest amides, formed by
• reaction between CO2 and ammonia in a series of
• metabolic reactions.
• Acetominophen is an aromatic amide
• Barbiturates derive from barbituric acid
• (sedatives/tranquilizers) are cyclic amides, made
• from urea and malonic acid

45

Physical properties of amides

• Amides do not have a basic non-bonding pair of
• electrons, like amines (as mentioned)
• The simplest amides (methanamide, N-methyl, and
• N,N-dimethyl derivatives) are liquids at room
• temperature, and all unbranched amides having 2
• or more carbons on their C-chain side are solids.
• The secondary and teritary amides have lower
• melting points, with tertiary amides having lower
• melting points than secondary amides (less
• opportunity for H-bonding).

46

Physical properties of amides

4 locations on a primary amide group that may

participate in intermolecular H-bonding

47

Preparation of amides

• Amides are prepared in a manner similar to what
• weve already seen for esters. A condensation
• reaction involving a carboxylic acid is needed,
• this time with an amine

48

Preparation of amides

• For amide formation to happen, the temperature
• must be high (at room temperature, an acid-base
• neutralization reaction happens instead).
• Also, the amine used in the reaction must be
• either a primary or secondary amine (cant be a
• tertiary amine).

49

Preparation of amides

• Ammonia carboxylic acid ? 1o amide
• 1o amine carboxylic acid ? 2o amide
• 2o amine carboxylic acid ? 3o amide

50

Preparation of amides

• Reactions that make esters from carboxylic acids
• and alcohols are called esterification reactions.
• Reactions that make amides from carboxylic acids
• and amines (or ammonia) are called amidification
• reactions. Thus amidification reactions are
• condensation reactions.
• In the condensation, the carboxylic acid loses
• the OH and the amine loses a H atom

51

Hydrolysis of amides

• Like esters, amides can undergo hydrolysis. This
• reaction results in the amide being broken up
• into amine and carboxylic acid starting
• materials

 

 

52

Hydrolysis of amides

• The products of the hydrolysis reaction will
• depend on the acidity/basicity of the reaction
• conditions.

acidic/basic conditions used

Remember what an acid does donates protons (H

ions) bases accept protons. Acids react with

bases, not with other acids.

53

Hydrolysis of amides

• Under basic conditions, the carboxylic acid is
• produced as an carboxylic acid salt

Remember, carboxylic acids are acids

amines are bases

Amide hydrolysis carried out under

basic conditions is called amide saponification.

54

Hydrolysis of amides

• Overall, the reaction would look like this
• Example

55

Hydrolysis of amides

• Under acidic conditions, the amine is produced as
• an ammonium salt

Remember, carboxylic acids are acids

amines are bases

56

Hydrolysis of amides

• Overall, under acidic conditions, the reaction
• would look like this
• Example

57

Polyamides

• Like we saw for esters, amide condensation
• reactions can be used to make polymers (another
• polycondensation reaction).
• As for polyesters, di-functional reactants are
• needed for polymerization (i.e. a diamine and a
• dicarboxylic acid)

58

Polyamides

• Nylon-6,6 is a polyamide. It can be synthesized
• from Hexanedioic acid and 1,6-Hexanediamine

59

Polyamides

• Kevlar (bullet-proof
• vests) is also a
• polyamide