The most common medical ester is aspirin (ASA; acetyl salicylic acid). Other drugs such as Worm Guard (anti-wormer), Maxicaine (local anesthetic), Malathion (organophosphate), Mebendazole (antihelmenthic), Demerol (narcotic analgesic) and Equinil (sedative) are also esters.
The starting reactants for this experiment are salicylic acid and acetic anhydride (structures are shown above).

Salicylic acid reacts better with acetic anhydride than acetic acid, so acetic acid will provide the acetyl group which will react with the alcoholic -OH group on the salicylic acid. (The reaction is on the top of the post.)

Chemicals needed for the reaction: Salicylic acid, Acetic anhydride, and Concentrated sulfuric acid.

Equipment: 250 mL Erlenmeyer flask, Hot water bath, Ice bath, Buchner funnel and filter paper, Glass stirring rod, and Electronic pan balance and weighing boat.

There are four types of reactions:

Substitution Reactions

The reactions in which an atom or group of atoms in a molecule is replaced or substituted by different atoms or group of atoms are called substitution reaction. For example,

These reactions can be of two types:

Nucleophilic Substitution

In this type of substitution, atom or group of atoms in the molecule is replaced by a nucleophile. These can be either S_N1 (substitution, nucleophilic, unimolecular) or S_N2 (substitution, nucleophilic, bimolecular) type.
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Let’s look at some chemical structures:
One problem occurs with aspirin is that it has a destructive effect on the blood vessel walls and inhibit the synthesis of prostacyclin. To resolve this problem, we can use potential anti-platelet agents including the O-acyl esters which are synthesized from salicylic acid and diflunisal. Those agents work by acylation of cyclooxygenase and have a higher extraction than aspirin. That makes them yield a greater selectivity in their effect on platelet inhibition relative to prostacyclin inhibition on vessel walls.

The actual reaction is shown on the top.

Alkenes are named as if they were alkanes, but the “-ane” suffix is changed to “-ene”. If the alkene contains only one double bond and that double bond is terminal (the double bond is at one end of the molecule or another) then it is not necessary to place any number in front of the name.

butane: C₄H₁₀ (CH₃CH₂CH₂CH₃)
butene: C₄H₈ (CH₂=CHCH₂CH₃)

If the double bond is not terminal (if it is on a carbon somewhere in the center of the chain) then the carbons should be numbered in such a way as to give the first of the two double-bonded carbons the lowest possible number, and that number should precede the “ene” suffix with a dash, as shown below.

correct: pent-2-ene (CH₃CH=CHCH₂CH₃)
incorrect: pent-3-ene (CH₃CH₂CH=CHCH₃)
The second one is incorrect because flipping the formula horizontally results in a lower number for the alkene.

If there is more than one double bond in an alkene, all of the bonds should be numbered in the name of the molecule – even terminal double bonds. The numbers should go from lowest to highest, and be separated from one another by a comma. The IUPAC numerical prefixes are used to indicate the number of double bonds.
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DNA Double Helix: A Recent Discovery of Enormous Complexity
The DNA Double Helix is one of the greatest scientific discoveries of all time. First described by James Watson and Francis Crick in 1953, DNA is the famous molecule of genetics that establishes each organism’s physical characteristics. It wasn’t until mid-2001, that the Human Genome Project and Celera Genomics jointly presented the true nature and complexity of the digital code inherent in DNA. We now understand that each human DNA molecule is comprised of chemical bases arranged in approximately 3 billion precise sequences. Even the DNA molecule for the single-celled bacterium, E. coli, contains enough information to fill all the books in any of the world’s largest libraries.
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