SELAMAT DATANG


Kamis, 07 Juni 2012

When the amide is hydrolyzed in acidic conditions, acid proton of the carbonyl oxygen, increase the susceptibility of the carbonyl carbon to nucleophilic attack. Nucleophilic attack by water on the carbonyl carbon causes the tetrahedral intermediate compound I, which is in equilibrium with form rather than protons, tetrahedral intermediate II. Reprotonasi can occur either at the tetrahedral intermediates of oxygen to reform I ataupada nitrogen to form a tetrahedral intermediate III. Protonation at nitrogen is preferred because the NH2 group is a stronger base than OH groups. Of the two possible groups to go on a tetrahedral intermediate III group (-OH danNH3), NH3 is a weak base, so it is released, forming carboxylic acids as end products. Because the reaction is carried out in acid solution, NH3 be protonated after expelled from the tetrahedral intermediates. This prevents the reverse reaction.

This revelation may be able to answer the question from Mr. Syam, the production amount of carboxylic acid in acidic conditions far more than under base conditions.
PROBLEM
1. why amide does'nt reactive?
2. Why can not hydrolyze amide without a catalyst?
  
  answer :  
  1. Amide is a compound that is not reactive, since the protein consists of amino acids linked by amide bonds. Amide does not react with halide ions, ionkarboksilat, alcohol, or water because in each case, the incoming nucleophile is basalemah of the amide group to go. Amide can react with water and alcohol if the reaction mixture was heated dalamsuasana asam.Teori molecular orbitals may explain why the amide is not reactive. Amide resonance memilikikontributor important where one partner shares with karbonkarbonil nitrogen, which contains a lone pair orbital overlap of the vacant orbital overlap guguskarbonil.Keadaan lower-energy one partner is not a base or nucleophilic, and raises the energy of the orbital of the carbonyl group, resulting in less reactive terhadapnukleofil. Amide NH 2 groups can be dehydrated to a nitrile. Reagendehidrasi generally used for this purpose is P2O5, POCl3, and SOCl3.
  2. In the reaction without catalyst, amidatidak protonated. Therefore, the water, a very poor nucleophile, should be neutral menyerangamida far more susceptible to nucleophilic than serangandari amidaterprotonasi. In addition, the group of the tetrahedral intermediate is not protonated in the reaction without a catalyst. Therefore, the-OH group is away from the tetrahedral intermediate, because  -OH is a weak base of the -NH2 amide reform. A amidabereaksi with alcohol under acidic conditions for the same reason will bereaksidengan water under acidic conditions.


                                                                                                   
                                                       I’m sorry if there are mistakes

Preparation of amides:

Amides are generally synthesized in the laboratory in several ways:
1. Anhydride reaction with ammonia

2. Ester reaction with ammonia

3. Reaction of acid chlorides with ammonia

4. Heating ammonium carboxylate salts


Amide hydrolysis:
Amida is very strong / resistant to hydrolysis. But the presence of concentrated acid or base, hydrolysis can occur producing carboxylic acid.


Kamis, 31 Mei 2012

POLYAMIDE   
          A polyamide is a polymer containing monomers of amides joined by peptide bonds. They can occur both naturally and artificially, examples being proteins, such as wool and silk, and can be made artificially through step-growth polymerization or solid-phase synthesis, examples being nylons, aramids, and sodium poly(aspartate). Polyamides are commonly used in textiles, automotives, carpet and sportswear due to their extreme durability and strength.

Classification
According to the composition of their main chain, polyamides are classified as follows:
Polyamide family
Main chain
Examples of polyamides
Examples of commercial products
Aliphatic polyamides
Aliphatic
PA 6 and PA 66
Semi-aromatic
Trogamid from Evonik Industries, Amodel from Solvay
Aramides = aromatic polyamides
Aromatic
Paraphenylenediamine + terephthalic acid
Kevlar and Nomex from DuPont, Teijinconex, Twaron and Technora from Teijin, Kermel from Kermel
According to the number of repeating units' types, polyamides can be:
  • homopolymers :
    • PA 6 : [NH−(CH2)5−CO]n made from ε-Caprolactam ;
    • PA 66 : [NH−(CH2)6−NH−CO−(CH2)4−CO]n made from hexamethylenediamine and adipic acid;
  • copolymers :
    • PA 6/66 : [NH-(CH2)6−NH−CO−(CH2)4−CO]n−[NH−(CH2)5−CO]m made from caprolactam, hexamethylenediamine and adipic acid ;
    • PA 66/610 : [NH−(CH2)6−NH−CO−(CH2)4−CO]n−[NH−(CH2)6−NH−CO−(CH2)8−CO]m made from hexamethylenediamine, adipic acid and sebacic acid.
According to their crystallinity, polyamides can be:
According to this classification, PA66, for example, is an aliphatic semi-crystalline homopolyamide.

Production from monomers
The amide link is produced from the condensation reaction of an amino group and a carboxylic acid or acid chloride group. A small molecule, usually water, or hydrogen chloride, is eliminated.
The amino group and the carboxylic acid group can be on the same monomer, or the polymer can be constituted of two different bifunctional monomers, one with two amino groups, the other with two carboxylic acid or acid chloride groups.
Amino acids can be taken as examples of single monomer (if the difference between R groups is ignored) reacting with identical molecules to form a polyamid                                                                              
The reaction of two amino acids. Many of these reactions produce long chain proteins
Aramid (pictured below) is made from two different monomers which continuously alternate to form the polymer and is an aromatic polyamide:

The reaction of 1,4-phenyl-diamine (para-phenylenediamine) and terephthaloyl chloride to produce Aramid

β-LACTAM ANTIBIOTIC
            β-Lactam antibiotics (beta-lactam antibiotics) are a broad class of antibiotics, consisting of all antibiotic agents that contains a β-lactam nucleus in their molecular structures. This includes penicillin derivatives (penams), cephalosporins (cephems), monobactams, and carbapenems. Most β-lactam antibiotics work by inhibiting cell wall biosynthesis in the bacterial organism and are the most widely used group of antibiotics. Up until 2003, when measured by sales, more than half of all commercially available antibiotics in use were β-lactam compounds.
Bacteria often develop resistance to β-lactam antibiotics by synthesizing a β-lactamase, an enzyme that attacks the β-lactam ring. To overcome this resistance, β-lactam antibiotics are often given with β-lactamase inhibitors such as clavulanic acid.

First Meeting

1. AMINES           

    Amines are organic compounds and functional groups whose contents consist of atomic nitrogen      compounds by the couple themselves. Amino is a derivative of ammonia. Usually called the amide and has a variety of different chemicals. Which includes amino acids are acids, biogenic acids, trimethylamine, and aniline.
   
The smell of ammonia, is an old fish, urine, Rotting flesh, and all the semen is composed of amino substances.



2.  AMIDA

     Amida is a type of chemical that can have two senses. The first type is an organic functional group having a carbonyl group (C = O), which binds to a nitrogen atom (N), or a compound that contains this functional group. The second kind is a form of nitrogen anion.
 3. LACTAM

     A lactam (the noun is a portmanteau of the words lactone + amide) is a cyclic amide. Prefixes indicate how many carbon atoms (apart from the carbonyl moiety) are present in the ring: β-lactam (2 carbon atoms outside the carbonyl, 4 ring atoms in total), γ-lactam (3 and 5 total), δ-lactam (4 and 6 total). Beta β, gamma γ and delta δ are the second, third and fourth letters in the alphabetical order of the Greek alphabet, respectively.





General synthetic methods exist for the organic synthesis of lactams.

  • Lactams form by copper catalyzed 1,3-dipolar cycloaddition of alkynes and nitrones in the Kinugasa reaction
  • Diels-Alder reaction between cyclopentadiene and chlorosulfonyl isocyanate (CSI) can be utilized to obtain both β- as well as γ-lactam. At lower temp (−78 °C) β-lactam is the preferred product. At optimum temperatures, a highly useful γ-lactam known as Vince Lactam is obtained.[2]