in StemSocial2 months ago

Greetings welcome dear readers, we continue to address the scientific topic related to the application of alkenes as a family belonging to organic chemistry, so that this time, we will be making a theoretical approach - practice about the chemistry of dienes and how through these compounds can be developed photolithographic processes.

In this sense and as has been constant in this popular science blog, it will be a content that we will share through the Stemsocial community where the approach to science from different disciplines is promoted.

Image courtesy of: vipulK007

Therefore, it should be noted that when talking about photolithography we refer to an industrial process where different systems or chemical processes are used to develop semiconductor devices that will be present in integrated circuits, theoretically this process consists of a proton transfer mechanism from a photo mask to the surface of a double disk or wafer, which is nothing more than a thin plate of semiconductor material with which the microcircuits will be developed or built.

Based on the above, through this industrial process, chemical principles are assumed in the first instance associated with ultraviolet spectroscopy and the synthesis and obtaining of organic products, where the presence of multiple bonds plays a determining role, so that throughout this system, dienes as organic compounds that usually alternate single bonds with conjugated double bonds, will be the starting point to give structure to the practical theoretical approach of this content.

So it is necessary to retake the processes of pigmentation that we addressed in previous publications, where we managed to mention that the pigments of the fruits and the diversity of colors that they present are chemically due to the beta carotenes that are present and that when chemically evaluating their structure, we can realize that they are chains where the double bonds are alternated and consequently large structures of conjugated polyenes are developed, an example of them is represented by lycopene, this being understood as a pigment that is characterized by the red color in tomatoes.

We can also find progesterone, which is assumed to be the hormone that prepares the uterus for the implantation of the fertilized egg. Another of the molecules that has had the greatest scientific boom is represented by 1, 3, 5 cyclohexatriene, also known as benzene, since it has a great practical utility in the industrial systems known so far, So that if we observe the following image we can denote that the bonds in benzene in spite of being conjugated are observed in continuous lines, which implies that they are in constant movement and alternate in resonant forms, a phenomenon that generates great stability to the molecule.

In relation to its synthesis, we can establish that conjugated dienes are prepared at industrial level through a process of induced elimination of an alkyl halide, an example of this is represented by the compound 1, 3-butadiene, a substance used in the manufacture of polymers, consequently this is prepared through the pyrolysis of butane on a chromium oxide catalyst and aluminum at a temperature of 600°C as seen in the reaction below:

With respect to the stability of the compounds, we have to establish that the number of increasing unsaturations is directly proportional to the stability of the compound, so that those conjugated dienes release less heat than mono or disubstituted alkenes and this is because we need to implement greater amounts of potential energy to initiate a reaction process in these compounds.

Starting from the previous property, conjugated dienes have the ability to polymerize generating much more complex compounds, if we compare them with the polymers of simple or normal alkenes, likewise dienes can generate and structural isomers of cis and trans types, an aspect that we have already addressed in previous publications.

Consequently, the process of generating polymers through these compounds starts with a reaction initiator, which can be a radical and an example of this occurs with the process of polymerization of ethylene or an acid, which responds to a simple addition reaction at carbon 1, 4 of the growing chain, either of a monomer or of a diene or conjugate.

So that from this reaction different polymers can be prepared, such is the case of natural rubber, which is an isoprene polymer of natural origin where the double bonds present in the molecule, manifest a stereochemistry (Z), which implies that the molecule has the ability to form different structure and spatial arrangements, and it is this spatial organization that provides the properties and potential of the polymer obtained.

So that the compound based on natural rubber has greater utility and applications in everyday life than synthetic rubber, however, synthetic rubber also known as gutta-percha is implemented as a coating in golf balls.

Now, once the technical aspects regarding the structure and properties of the conjugated systems have been conceived, it is necessary to highlight how this type of structure is determined and undoubtedly the way to do it through mass spectroscopy, infrared spectroscopy and nuclear magnetic resonance, These techniques are the ones that allow us to establish the degree of instaurations and the size of the organic molecule with which we are working, consequently, it is the advances in these analytical techniques and the improvement of photolithography techniques that have allowed us to generate better applications and use in technological processes and in the development of computational equipment.

To understand in more detail the scope of the general polymer process through diene, it is necessary to remember that more than 25 years ago, those who were interested in buying technological equipment such as computers, had to pay large amounts of money exceeding $150000 for barely a 16 megabyte random access memory that could occupy the space of a small desk.

Today, through scientific advances we can get a 16 megabyte memory for just under $30 and they are so tiny that we can keep them in our shirt pocket, no doubt the difference today with 25 years ago applies exclusively to advances and improvements in the photolithographic technique or otherwise in the process with which integrated circuits are manufactured.

Chemically, photolithography starts by applying a coating or a layer of silicon oxide to a silicon tablet, which will then be covered by a thin film of an organic polymer sensitive to ultraviolet light and through the cover is implemented another layer to cover the different components or part of the chip that will become a circuit, which will be subjected to a process of radiation with ultraviolet light.

So it is an intentional process and those sections of the polymer that have been uncovered are chemically attacked with the purpose of generating a change and an increase in solubility if we compare them with the non-irradiated regions, so that washing with the appropriate solvent this will be able to remove the solubilized polymer and thus expose the silicon components present, which through other coating and washing process allows to obtain the chip in a finished state and with the necessary protection for its operation. There is no doubt that it is a complex process that has allowed us to evolve in the world of science, technology and computing.


[1] Realpe and collaborators. Design and implementation of a photolithography system to fabricate microdevices from thin films.Artículo: Acceso Online

[2] Chang, R. (2010). Química. Decima edicion. McGraw-hill Interamericana editores. ISBN: 978-607-15-0307-7.

[3] Ralph, H. Petrucci, William S. Harwood, E. Geoffrey Herring. (2003). QUIMICA GENERAL. Octava edición. PEARSON EDUCACIÓN. S.A., Madrid.



1. The molecular models presented were designed by @madridbg using Chem3D and Chemdraw software.

2. For more information related to the areas of science, technology, engineering and mathematics, do not hesitate to visit #stemsocial and #stem-espanol, they are communities that promote scientific advances in these areas


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