Archives November 2013

 Modes of transmission OR Means Of Spread Of Communicable Diseases:Once an infectious agent leaves a reservoir, it must get transmitted to a new host if it is to multiply and cause disease. The route by which an infectious agent is transmitted from a reservoir to another host is called the mode of transmission. It is important for you to identify different modes of transmission, because prevention and control measures differ depending on the type. Direct modes of transmission Direct transmission refers to the transfer of an infectious agent from an infected host to a new host, without the need for intermediates such as air, food, water or other animals. Direct modes of transmission can occur in two main ways:

• Person to person: The infectious agent is spread by direct contact between people through touching, biting, kissing, sexual intercourse or direct projection of respiratory droplets into another person’s nose more...

The electrocardiograph—also known as EKG or ECG— is an instrument designed to record minute electric currents generated within the heart, which are used to diagnose different types of heart disease. At the end of the nineteenth century, physiologists understood that beating hearts produced electrical currents, but they could only measure them by placing electrodes directly on heart muscle. Dutch physician and physiologist Willem Einthoven (1860-1927) adapted the string galvanometer for use in cardiology. String galvanometers had first been used to amplify electrical signals transmitted along undersea cables. Einthoven's galvanometer, which he produced in 1903, consisted of a microscopic thread of quartz known as a "string" that was vertically suspended in a strong magnetic field. When minute currents passed through the string it deflected and obstructed a beam of light, allowing the shadow to be recorded on photographic paper. Early prototypes were unwieldy—weighing 600 pounds (272 kg), they needed to be more...

In this video Mr. Lalit Sardana(IIT-JEE AIR 243) an IITJEE trainer will be explaining you some topics like chain isomerism, position isomerism, functional isomerism, function isomerism, optical isomerism, metamerism in amines. He has done a lot of things that are above the call of duty. This video is useful for students appearing in 11th CBSE, 12th CBSE exams and for the students appering in the competitive exams like JEE Mains, JEE Advanced, VITEEE, WBJEE, KCET, J and K Engineering, MPPET, AIPMT. Watch the videos related to Isomerism in Amines through the following link http://www.studyadda.com/videos/jee-chemistry-lectures/amines/isomerism-in-amines/1432 

Amines are aliphatic and aromatic derivatives of ammonia. Amines, like ammonia, are weak bases (K b = 10 −4 to 10 −6). This basicity is due to the unshared electron pair on the nitrogen atom. Classification and nomenclature of amines Amines are classified as primary, secondary, or tertiary based upon the number of carbon‐containing groups that are attached to the nitrogen atom. Those amine compounds that have only one group attached to the nitrogen atom are primary, while those with two or three groups attached to the nitrogen atom are secondary and tertiary, respectively. Primary amines  In primary amines, only one of the hydrogen atoms in the ammonia molecule has been replaced. That means that the formula of the primary amine will be RNH2 where "R" is an alkyl group  Secondary amines  In a secondary amine, two of the hydrogens in an ammonia molecule have been replaced by hydrocarbon groups. At this more...

 In this video Mr. Lalit Sardana(IITJEE AIR 243) is explaining students about Hydrolysis of Chloroform which comes under Haloforms. This video is useful to the students appearing for 11th CBSE, 12th CBSE exams and competitive exams like IIT JEE, AIEEE, VITEEE, AIPMT, AFMC, EAMCET, WBJEE, KCET Engineering. Watch the videos related to the hydrolysis of chloroform through the following link http://www.studyadda.com/videos/jee-chemistry-lectures/haloforms/hydrolysis-of-chloroform/1430  

The Hofmann rearrangement is the organic reaction of a primary amide to a primary amine with one fewer carbon atom. By this method the amide (–CONH2) group is converted into primary amino (– NH2) group.   R - CO - NH2 + Br2 + 4KOH → R - NH2 + 2KBR + K2CO3 + 2H2O                 Amide                             Pri-amine      This is the most convenient method for preparing primary amines.   This method gives an amine containing one carbon atom less than amide. The reaction is named after its discoverer: August Wilhelm von Hofmann. This reaction is also sometimes called the Hofmann degradation or the Harmon Process, and should not be confused with the Hofmann elimination.   The reaction of bromine with sodium hydroxide forms sodium hypobromite in more...

Acetylene (systematic name: ethyne) is the chemical compound with the formula C2H2. It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is unstable in pure form and thus is usually handled as a solution. Pure acetylene is odorless, but commercial grades usually have a marked odor due to impurities. As an alkyne, acetylene is unsaturated because its two carbon atoms are bonded together in a triple bond. The carbon–carbon triple bond places all four atoms in the same straight line, with CCH bond angles of 180°. Since acetylene is a linear symmetrical molecule, it possesses the D∞h point group. Reaction with silver powder: On heating with silver powder, chloroform forms acetylene. Mr. Lalit Sardana (IITJEE AIR 243) is an IIT JEE educational trainer who has been teaching students since past many years. He is an experienced more...

  A haloform (CHX3, where X is a halogen) is produced by the exhaustive halogenation of a methyl ketone (a molecule containing the R–CO–CH3 group) in the presence of a base. R may be H, alkyl or aryl. The reaction can be used to produce chloroform (CHCl3), bromoform (CHBr3), or iodoform (CHI3).

• a compound derived from methane by substituting three hydrogen atoms by halogen atoms, e.g. chloroform.

Mr. Lalit Sardana(IIT-JEE AIR 243) will help you to discover more through this video. He will explain haloforms to you in detail and if you find something difficult then you may drop your comments or questions in the comment box or Ask module respectively. This topic is asked in 11th CBSE, 12th CBSE, JEE Mains, JEE Advanced, VITEEE, AIPMT, AFMC, MPPET, CET, KCET,etc.    Watch the video related to the following topic on this link http://www.studyadda.com/videos/jee-chemistry-lectures/haloforms/haloform/1427

The haloform reaction is a chemical reaction where a haloform (CHX3, where X is a halogen) is produced by the exhaustive halogenation of a methyl ketone (a molecule containing the R–CO–CH3 group) in the presence of a base. R may be H, alkyl or aryl. The reaction can be used to produce chloroform (CHCl3), bromoform (CHBr3), or iodoform (CHI3).  1) When methyl ketones are treated with the halogen in basic solution, polyhalogenaton followed by cleavage of the methyl group occurs. 2) The products are the carboxylate and trihalomethane, otherwise known as haloform. 3) The reaction proceeds via successively faster halogenations at the α-position until the 3 H have been replaced. 4) The halogenations get faster since the halogen stablises the enolate negative charge and makes it easier to form. 5) Then a nucleophilic acyl substitution by hydroxide displaces the anion CX3 as a leaving group that rapidly protonates. 6) This more...

The further detail on Gabriel phthalimide reaction will be given to you by Mr, Lalit Sardana (IIT-JEE AIR 243) who has been running a tutorial house since past many years and this tutorial house has a history of bringing up maximum number of IIT selections from the city. He is an exceptional teacher and here he is teaching you Gabriel phthalimide reaction using phthalic acid . This video is helpful for the students appearing for 11th CBSE, 12th CBSE, JEE Mains, JEE Advanced, KCET, VITEEE, J and K Engineering exams. Watch the Videos related to the Gabriel Phthalamide Reaction in the following link http://www.studyadda.com/videos/jee-chemistry-lectures/haloforms/gabriel-phthalimide-synthesis/1425