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PHYSICAL PROPERTIES OF BENZENE Benzene is a colourless liquid at room temperature. Has a peculiar smell and burning taste. Specific gravity, 0.8788. Melting point 5.5⁰C. Boiling point 80.2⁰C. Highly inflammable and burns with a smoky flame. Insoluble in water but soluble in either, alcohol and petrol. Used as a solvent for resins and fats. Benzene is a natural constituent of crude oil. Vapors of benzene are cancer producing (Carcinogenic).

Sources Acetylene is a hot-burning fuel used in welding torches.. Cicutoxin is a toxin found in water hemlock flowers. The simplest of the  alkyne  series, it is commonly called acetyline. It is often used as a fuel for welding torches sinces it produces a large amount of heat upon combustion. Oxyacetylene welding uses compressed acetylene and compressed oxygen for mixing in the torch flame . An exhaustive list would be hard to make, but if you put calcium carbide in water, the gas that comes off is an alkyne (ethyne, more commonly called acetylene) C2H2

Alkynes in nature and medicine According to Ferdinand Bohlmann, the first naturally occurring acetylenic compound, dehydromatricaria ester, was isolated from an Artemisia  species in 1826 . Polyynes, a subset of this class of natural products, have been isolated from a wide variety of plant species, cultures of higher fungi, bacteria, marine sponges, and corals.  Some acids like  tariric acid  contains an alkyne group. Diynes and triynes, species with the linkage RC ≡ C-C ≡ CR' and RC ≡ C-C ≡ C-C ≡ CR' respectively, occur in certain plants ( Ichthyothere , Chrysanthemum ,  Cicuta ,  Oenanthe  and other members of the  Asteraceae  and  Apiaceae  families).  Some examples are  cicutoxin , oenanthotoxin ,  falcarinol  and  carotatoxin . These compounds are highly bioactive, e.g. as  nematocides .  1-Phenylhepta-1,3,5-triyne is illustrative of a naturally occurring triyne. Alkynes occ...

The Variables of Organic Reactions In an effort to understand how and why reactions of functional groups take place in the way they do, chemists try to discover just how different molecules and ions interact with each other as they come together. To this end,  it is important to consider the various properties and characteristics of a reaction that may be observed and / or measured as the reaction proceeds  . The most common and useful of these are listed below: 1. Reactants and Reagents A. Reactant Structure:   Variations in the structure of the reactant may have a marked influence on the course of a reaction, even though the functional group is unchanged. Thus, reaction of 1-bromopropane with sodium cyanide proceeds smoothly to yield butanenitrile, whereas 1-bromo-2,2-dimethylpropane fails to give any product and is recovered unchanged. In contrast, both alkyl bromides form Grignard reagents (RMgBr) on reaction with magnesium. B. Reagent Character...

Classifying Organic Chemical Reactions If you scan any organic textbook you will encounter what appears to be a very large, often intimidating, number of reactions. These are the "tools" of a chemist, and to use these tools effectively, we must organize them in a sensible manner and look for patterns of reactivity that permit us make plausible predictions. Most of these reactions occur at special sites of reactivity known as functional groups, and these constitute one organizational scheme that helps us catalog and remember reactions. Ultimately, the best way to achieve proficiency in organic chemistry is to understand how reactions take place, and to recognize the various factors that influence their course. This is best accomplished by perceiving the reaction pathway or mechanism of a reaction. 1. Classification by Structural Change First, we identify four broad classes of reactions based solely on the  structural change  occurring in the reactant mol...

Chemical Reactivity Organic chemistry encompasses a very large number of compounds ( many millions ), and our previous discussion and illustrations have focused on their structural characteristics. Now that we can recognize these actors ( compounds ), we turn to the roles they are inclined to play in the scientific drama staged by the multitude of chemical reactions that define organic chemistry. We begin by defining some basic terms that will be used frequently as this subject is elaborated. Chemical Reaction:   A transformation resulting in a change of composition, constitution and/or configuration of a compound ( referred to as the reactant or substrate ). Reactant or Substrate:   The organic compound undergoing change in a chemical reaction. Other compounds may also be involved, and common reactive partners ( reagents ) may be identified. The reactant is often ( but not always ) the larger and more complex molecule in the reacting system. Most ( or all ) of the...

Mechanisms Of Organic Reactions A detailed description of the changes in structure and bonding that take place in the course of a reaction, and the sequence of such events is called the   reaction mechanism . A reaction mechanism should include a representation of plausible electron reorganization, as well as the identification of any intermediate species that may be formed as the reaction progresses. These features are elaborated in the following sections. 1. The Arrow Notation in Mechanisms Since chemical reactions involve the breaking and making of bonds, a consideration of the movement of bonding ( and non-bonding ) valence shell electrons is essential to this understanding. It is now common practice to show the movement of electrons with curved arrows, and a sequence of equations depicting the consequences of such electron shifts is termed a  mechanism . In general, two kinds of curved arrows are used in drawing mechanisms: A full head on the arrow ind...

In an effort to understand how and why reactions of functional groups take place in the way they do, chemists try to discover just how different molecules and ions interact with each other as they come together. To this end,   it is important to consider the various properties and characteristics of a reaction that may be observed and / or measured as the reaction proceeds  . The most common and useful of these are listed below:                                           1. Reactants and Reagents A. Reactant Structure :   Variations in the structure of the reactant may have a marked influence on the course of a reaction, even though the functional group is unchanged. Thus, reaction of 1-bromopropane with sodium cyanide proceeds smoothly to yield butanenitrile, whereas 1-bromo-2,2-dimethylpropane fails to give any product and is recovered unchanged. In contra...

Classifying Organic Chemical Reactions If you scan any organic textbook you will encounter what appears to be a very large, often intimidating, number of reactions. These are the "tools" of a chemist, and to use these tools effectively, we must organize them in a sensible manner and look for patterns of reactivity that permit us make plausible predictions. Most of these reactions occur at special sites of reactivity known as   functional groups , and these constitute one organizational scheme that helps us catalog and remember reactions.   Ultimately, the best way to achieve proficiency in organic chemistry is to understand how reactions take place, and to recognize the various factors that influence their course . This is best accomplished by perceiving the reaction pathway or mechanism of a reaction.                         1. Classification by Structural Change First, we identify four broad classes of...