ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

A Level Organic Chemistry Notes: Refining crude oil, definition of cis/trans, geometrical isomerism, hydrocarbon types

Updated on June 18, 2012

Importance of Carbon in Organic Chemistry

In organic chemistry, carbon (C) is the most important element. It has remarkable properties, which allow carbon a great diversity of combinations and bonds with other molecules.
Carbon has four valence electrons. This means that it can make four covalent bonds with other molecules. Also, it has a moderate electronegativity and a rather small (right) size. So, it can bond to other molecules easily and to itself and make infinite structures. Double bonds or even triple bonds are also possible with the carbon atom.

Definition of an organic molecule (definition of organic chemistry)

An organic molecule consists of many carbons and hydrogen atoms, which form bonds with the carbons. In addition, it has functional groups attached to the whole complex. The carbon-hydrogen bonds are assumed to be neutral as the difference in electronegativity is practically neutral anyway. Functional groups make up the polar part of an organic molecule.

There are different types of hydrocarbon molecules:

Aromatic hydrocarbon: These are hydrocarbon rings, which have double or triple bonds.
Saturated hydrocarbon: The formula of the hydrogen-carbon ratio is given by: CnH2n+2 , assuming a non-cyclic (ring) structure. Saturated hydrocarbons only consist of single bonds and the very easiest appearance of a saturated hydrocarbon is an alkane.
Unsaturated hydrocarbon: The ratio of hydrogen and carbon is given by: CnH2n , where again a non-cyclic structure is assumed. Unlike saturated hydrocarbons, it has double bonds and the simplest appearance of an unsaturated hydrocarbon is an alkene.
There is a second type of unsaturated hydrocarbons which has the ration formula given by: CnH2n-2. Once again, a non-cyclic structure is assumed and this type of hydrocarbon only makes triple bonds. The simplest structure is an alkyne.
Cyclic hydrocarbons are quite similar to aromatic hydrocarbons. Both are rings, but the difference lies in the bonds. Cyclic hydrocarbons only have saturated rings (only single bonds).

Crude oil refinery / refining process of oil / steps in manufacturing crude oil

The process of turning crude oil into a useful form is done in a crude oil refinery. The steps for making crude oil into oil, petrol or whatsoever are fractional distillation, cracking and reforming.


Step One of refining crude oil: Fractional distillation

The mixture is inserted at the bottom, where mostly everything will condense as the temperature is 350°C and more. The condensed crude oil will rise to the next fraction above, which has a very high temperature as well, but a slightly smaller one. Only the part of the mixture, which boiling point is under the temperature of the fraction, will condense and rise to the next fraction. The part of the mixture, whose boiling point is higher than the temperature inside the distillation fraction, will stay there and be pumped out.

Example: Supposing the temperature inside the current fraction is 300°C. The part of the mixture, which boiling point is less than 300°C, will condense. Only the molecules, which have a boiling point over 300°C, will remain in the fraction. That process is repeated about 50 to 60 times in total.


Step Two of refining crude oil: Cracking

After the fractional distillation process, the separated mixtures have to be cracked down. This means that a long molecule will be split up in smaller parts. How does one achieve this?
Firstly, single bonds will be broken down. This results into some lone electrons.
The lone electrons form double bonds. Thus, hydrogen will disconnect from the carbon atom. Hydrogen (H2) remains as a side product. The loss of hydrogen in these smaller organic molecules is logical, because when they are lost, more lone electrons remain with what the previous lone electrons can make a bond.

Step Three of refining crude oil: Reforming

After cracking, the molecules are ready to undergo the reforming process.
This is given by the octane number. The octane number is very important in petrol. It tells what the percentage of pure heptane (in the earlier days it was octane – that is why it is called octane number) in petrol is. This is of great importance for the chemical behaviour. The quality of petrol is improved by adding mixtures to pure heptane. The chains of heptane are heated up (where platinum is used as a catalyst). So they can change. After the heating process, it shows a higher amount of branched chains. This increases the octane number.

Example: When the petrol you buy has a 98 in the name, then it means that 98% are branched chains and 2% of the mixture is pure heptane (or another pure molecule).

Different forms of Isomerism

Isomers are compounds of with the same molecular formula, but with different structural formulas (means: they look different). Isomers do not necessarily share the same chemical properties (like boiling point, reactivity etc.)


Definition of structural isomerism

Two organic molecules which have the same chemical formula but look different. For example, C2H6O can be drawn as C2H5OH or CH3OCH3 (see picture below). Both look differently and have completely different chemical properties.


Definition of cis / trans isomer pairs

A cis/trans pair has the same molecular formula but their build-up is only slightly different, depending upon the position of the heaviest molecules.
The cis isomer has its heaviest molecules on the same side of a double bond (or a ring system).
The trans isomer has not its heaviest molecules on the same side of a double bond (or a ring system). Those two isomers make up the cis/trans isomer pair.
This does not work on single bonds, since the molecule would be considered as flexible and can so turn around its axis.


Definition of chiral molecules

Chirality is another form of isomerism. If a molecule is mirrored and its mirror image is the same as the original molecule, then it is achiral and therefore the two molecules are identical.
If the mirror molecule is unlike the original molecule, then they are chiral and therefore not identical. This is the case if the molecules have no plane of symmetry (see picture).


Definition of enantiomers

Enantiomers are molecules which look very similar, but are not superimposable. Supposing we have a molecule A which is mirrored, giving us molecule B. If there is a molecule A’ which is moved about 180° and is not superimposable on the resulting molecule B, then those two are enantiomers (see picture). Its difference lies often in the orientation of the bonds whether they are pointing outwards or pointing inwards the room.


For the production of esters only a carboxyl and an alcohol are needed.
carboxyl + alcohol => ester + side product
R-CO2H + R’-OH ó R-CO2-R’ + H2O (or another side product)


    0 of 8192 characters used
    Post Comment

    No comments yet.


    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at:

    Show Details
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the or domains, for performance and efficiency reasons. (Privacy Policy)
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)