Chemistry

This chemical reaction mechanism drawing depicts steps of carbonyl compound halogenation reaction.
"Alpha-substitution reactions occur at the position next to the carbonyl group, the α-position, and involve the substitution of an α hydrogen atom by an electrophile, E, through either an enol or enolate ion intermediate. ...
Alpha Halogenation of Aldehydes and Ketones.
A particularly common α-substitution reaction in the laboratory is the halogenation of aldehydes and ketones at their α positions by reaction Cl2, Br2 or I2 in acidic solution. Bromine in acetic acid solvent is often used. ...
The halogenation is a typical α-substitution reaction that proceeds by acid catalyzed formation of an enol intermediate." [Carbonyl Alpha-Substitution Reactions. Wikipedia]
This example was redesigned from the Wikimedia Commons file: Halogenierung Mechanismus Version 3-Seite001.svg. [commons.wikimedia.org/ wiki/ File:Halogenierung_ Mechanismus_ Version_ 3-Seite001.svg]
This image is available under the Creative Commons Attribution-ShareAlike 3.0 Unported License. [creativecommons.org/ licenses/ by-sa/ 3.0/ ]
The chemical drawing example "Carbonyl compound halogenation mechanism" was created using the ConceptDraw PRO diagramming and vector drawing software extended with the Chemistry solution from the Science and Education area of ConceptDraw Solution Park.

The vector stencils library "Aromatics" contains 23 symbols of aromatic rings for chemical drawing of molecular structural formulas and reaction mechanism schemes in organic chemistry.
"In organic chemistry, aromaticity is a chemical property describing the way in which a conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibits a stabilization stronger than would be expected by the stabilization of conjugation alone. ... Aromaticity can also be considered a manifestation of cyclic delocalization and of resonance. This is usually considered to be because electrons are free to cycle around circular arrangements of atoms that are alternately single- and double-bonded to one another. These bonds may be seen as a hybrid of a single bond and a double bond, each bond in the ring identical to every other. This commonly seen model of aromatic rings, namely the idea that benzene was formed from a six-membered carbon ring with alternating single and double bonds (cyclohexatriene), was developed by Kekulé (see History section below). The model for benzene consists of two resonance forms, which corresponds to the double and single bonds superimposing to give rise to six one-and-a-half bonds. Benzene is a more stable molecule than would be expected without accounting for charge delocalization. ... Types of aromatic compounds. The overwhelming majority of aromatic compounds are compounds of carbon, but they need not be hydrocarbons. 1. Neutral homocyclics. Benzene, as well as most other annulenes (cyclodecapentaene excepted) with the formula CnHn where n is an even number, such as cyclotetradecaheptaene. 2. Heterocyclics. In heterocyclic aromatics (heteroaromats), one or more of the atoms in the aromatic ring is of an element other than carbon. This can lessen the ring's aromaticity, and thus (as in the case of furan) increase its reactivity. Other examples include pyridine, pyrazine, imidazole, pyrazole, oxazole, thiophene, and their benzannulated analogs (benzimidazole, for example). 3. Polycyclics. Polycyclic aromatic hydrocarbons are molecules containing two or more simple aromatic rings fused together by sharing two neighboring carbon atoms (see also simple aromatic rings). Examples are naphthalene, anthracene, and phenanthrene. 4. Substituted aromatics. Many chemical compounds are aromatic rings with other functional groups attached. Examples include trinitrotoluene (TNT), acetylsalicylic acid (aspirin), paracetamol, and the nucleotides of DNA. 5. Atypical aromatic compounds. Aromaticity is found in ions as well: the cyclopropenyl cation (2e system), the cyclopentadienyl anion (6e system), the tropylium ion (6e), and the cyclooctatetraene dianion (10e). Aromatic properties have been attributed to non-benzenoid compounds such as tropone. Aromatic properties are tested to the limit in a class of compounds called cyclophanes. A special case of aromaticity is found in homoaromaticity where conjugation is interrupted by a single sp³ hybridized carbon atom. When carbon in benzene is replaced by other elements in borabenzene, silabenzene, germanabenzene, stannabenzene, phosphorine or pyrylium salts the aromaticity is still retained. Aromaticity also occurs in compounds that are not carbon-based at all. Inorganic 6-membered-ring compounds analogous to benzene have been synthesized. Hexasilabenzene (Si6H6) and borazine (B3N3H6) are structurally analogous to benzene, with the carbon atoms replaced by another element or elements. In borazine, the boron and nitrogen atoms alternate around the ring." [Aromaticity. Wikipedia]
The organic compound structural formulas example "Aromatics - Vector stencils library" was created using the ConceptDraw PRO software extended with the Chemistry solution from the Science and Education area of ConceptDraw Solution Park.

The vector stencils library "Chemical drawings" contains 81 symbols of organic compounds and functional groups for chemical drawing.
Use it to draw structural formulas of organic molecules, schemes of chemical reactions and organic chemistry diagrams.
"Structural drawings.
Organic molecules are described more commonly by drawings or structural formulas, combinations of drawings and chemical symbols. The line-angle formula is simple and unambiguous. In this system, the endpoints and intersections of each line represent one carbon, and hydrogen atoms can either be notated explicitly or assumed to be present as implied by tetravalent carbon. The depiction of organic compounds with drawings is greatly simplified by the fact that carbon in almost all organic compounds has four bonds, nitrogen three, oxygen two, and hydrogen one. ...
Organic reactions.
Organic reactions are chemical reactions involving organic compounds. While pure hydrocarbons undergo certain limited classes of reactions, many more reactions which organic compounds undergo are largely determined by functional groups. The general theory of these reactions involves careful analysis of such properties as the electron affinity of key atoms, bond strengths and steric hindrance. These issues can determine the relative stability of short-lived reactive intermediates, which usually directly determine the path of the reaction.
The basic reaction types are: addition reactions, elimination reactions, substitution reactions, pericyclic reactions, rearrangement reactions and redox reactions. ...
Each reaction has a stepwise reaction mechanism that explains how it happens in sequence - although the detailed description of steps is not always clear from a list of reactants alone.
The stepwise course of any given reaction mechanism can be represented using arrow pushing techniques in which curved arrows are used to track the movement of electrons as starting materials transition through intermediates to final products." [Organic chemistry. Wikipedia]
The chemical symbols example "Design elements - Chemical drawings" was created using the ConceptDraw PRO software extended with the Chemistry solution from the Science and Education area of ConceptDraw Solution Park.