ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

Anomeric Effect

Updated on December 29, 2012
When Y has a pair of electrons (any heteroatom usually oxygen, sulfur or nitrogen), X (any hydroxy group O-X) prefers axial position
When Y has a pair of electrons (any heteroatom usually oxygen, sulfur or nitrogen), X (any hydroxy group O-X) prefers axial position
When Y has a pair of electrons, X prefers Gauche orientation. Y and X definition follow the same as the first statement.
When Y has a pair of electrons, X prefers Gauche orientation. Y and X definition follow the same as the first statement.
When Y has electrons it has a dipole in the same direction as the X, dipole moments create instability and create net dipole moment. X becomes axial and as a result changes direction and net dipole. Y and X definition follow the same as the first sta
When Y has electrons it has a dipole in the same direction as the X, dipole moments create instability and create net dipole moment. X becomes axial and as a result changes direction and net dipole. Y and X definition follow the same as the first sta

What is Anomeric Effect? It states that an axial anomer is more stable than the equatorial anomer. Well what is a anomer? An anomer is a cyclic stereoisomer, in many cases an alpha or beta stereoisomer of a pyranose form of a sugar. The reason why the axial position is preferred is simply because in an equatorial configuration there is a presence of dipole with any atom that isn’t a carbon or hydrogen, or a heteroatom. The dipoles of the heteroatom and the hydroxy group become parallel in such a way that it causes repulsion between atoms which is not good for the stability of the molecule. Now in axial position the dipoles points the other way, and as a result this is a good stabilizing effect for the molecule. The hydroxy group as a result adopts a gauche orientation. The carbon from which the hydroxy group becomes axial is known as the anomeric carbon. Now you might say, do not groups on a cyclohexane ring want to be in an equatorial position to relieve steric strain? This may be true, but when a heteroatom joins adjacent to a group like a hydroxyl group, the hydroxyl group becomes axial regardless of the steric strain, as stability of the entire molecule is important than mere strains. This is supported by numerous experiments done throughout the 50’s. The second reason why axial position is preferred has to do with delocalization of electrons. Delocalization provides stability because the electrons are able to move based on surrounding charges to better provide stability. When you have a heteroatom like oxygen with lone pairs in axial position, the electrons are able to move around with the electrons of the hydroxyl group that are also in axial position. This lowers the overall reactive energy of the molecule and provides great stability to the molecule. Now you might ask why doesn’t an every C-H group become axial if it provides better stability. Well it is because C-H groups aren’t good electron donors, heteroatoms are better donors because in many cases they’re rich in electrons and have high electronegativity. How the effect came to be discovered is quite interesting. John T. Edward and Raymond Lemieux in 1956 were studying carbohydrate chemistry, and they noticed how in acetyl group (COCH3) and in alkoxy group (R-O) groups like (CH3O-), tended to have a high percentage of axial positions. Upon studying and experimenting they came up with the postulate that it was the lone pairs from the oxygen that had played a role in the effect. Edward credits Lemieux with coming up with the name.

Bibliography:

1) Juaristi, E.; Cuevas, G. The Anomeric Effect, CRC Press: BOca Raton, 1995.

2) G.R.J. Thatcher (ed.), The Anomeric Effect and Related Stereolectronic Effects. ACS Symposium Series #539, 1993.

3) Juaristi, E., Cuevas, G., Tetrahedron, 1992, 48(24), 5019-5087.

4) Edward, John T. The Anomeric Effect and Associated Stereoelectronic Effects, Chapter 1: Anomeric Effect How It Came To Be Postulated, 1993, pp 1-5. ACS Symposium Series, Volume 539

Watch 6:25 min into the video to hear about Anomers

Did this help you?

See results

Cite this page

MLA Format

Soman, Stanley. "Anomeric Effect." ExpertsColumn on HubPages. HubPages, 25 Dec. 2012. Web. 27 Dec. 2012(Replace with the date of your access). <http://expertscolumn.hubpages.com/hub/Anomeric-Effect>.

APA Format

Soman, S. (2012, December 25). Anomeric Effect. ExpertsColumn on HubPages. Retrieved December 27, 2012(Replace with the date of your access), from http://expertscolumn.hubpages.com/hub/Anomeric-Effect

Comments

    0 of 8192 characters used
    Post Comment

    No comments yet.

    working

    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, hubpages.com 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: https://hubpages.com/privacy-policy#gdpr

    Show Details
    Necessary
    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 googleapis.com or gstatic.com domains, for performance and efficiency reasons. (Privacy Policy)
    Features
    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)
    Marketing
    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.
    Statistics
    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)