14.4 Hemiacetals and Acetals Maltose, a disaccharide, is

14.4 Hemiacetals and Acetals Maltose, a disaccharide, is

14.4 Hemiacetals and Acetals Maltose, a disaccharide, is produced from the hydrolysis of the starches in grains, such as barley. In maltose, an acetal bond links two glucose molecules. Learning Goal Draw the condensed or line-angle structural formulas for the products of the addition of alcohols to aldehydes and ketones. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake

2016 Pearson Education, Inc. Hemiacetal and Acetal When one alcohol adds to an aldehyde or ketone in the presence of an acid catalyst, the product is a hemiacetal. Hemiacetals contain two functional groups on the same carbon atom, a OH group and an OR group. Hemiacetals are generally unstable and react with a second molecule of the alcohol to form a stable acetal and water. Acetals contain two alkoxy ( OR) groups on the same carbon atom.

General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake 2016 Pearson Education, Inc. Hemiacetal and Acetal Formation Commercially, compounds that are acetals are used to produce vitamins, dyes, pharmaceuticals, and perfumes. Aldehydes are often more reactive than ketones because the carbonyl carbon is more positive. The presence of two alkyl groups in ketones makes it more difficult for an alcohol to form a bond with the carbon in the carbonyl group.

General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake 2016 Pearson Education, Inc. Hemiacetal and Acetal Formation The reactions in the formation of hemiacetals and acetals are reversible. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake 2016 Pearson Education, Inc.

Cyclic Hemiacetals One very important type of hemiacetal that can be isolated is a cyclic hemiacetal that forms when the carbonyl group and the OH group are in the same molecule. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake 2016 Pearson Education, Inc. Formation of Cyclic Hemiacetals

Five- and six-atom cyclic hemiacetals and acetals are more stable than their open-chain isomers. Glucose forms a six-carbon cyclic hemiacetal when the hydroxyl group on carbon 5 bonds with the carbonyl group on carbon 1. The hemiacetal of glucose is so stable that almost all the glucose exists as the cyclic hemiacetal in aqueous solution. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake 2016 Pearson Education, Inc.

Glucose Forms a Cyclic Hemiacetal General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake 2016 Pearson Education, Inc. Alcohol Adds to a Cyclic Hemiacetal An alcohol can add to the cyclic hemiacetal and form a cyclic acetal. This reaction explains how sugar molecules can link together and form disaccharides and polysaccharides.

General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake 2016 Pearson Education, Inc. Glucose + Glucose = Maltose Maltose is a disaccharide consisting of two glucose molecules. an acetal bond (shown in red) that links two glucose molecules. One carbon atom in glucose retains the cyclic hemiacetal bond (shown in green).

General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake 2016 Pearson Education, Inc. Study Check Identify each as a hemiacetal or an acetal. A. B. General, Organic, and Biological Chemistry: Structures of Life, 5/e

Karen C. Timberlake 2016 Pearson Education, Inc. Study Check Identify each as a hemiacetal or an acetal. A. hemiacetal B. acetal

General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake 2016 Pearson Education, Inc. Study Check Draw the condensed structural formula of the acetal formed by adding CH3OH to butanal. General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake

2016 Pearson Education, Inc. Solution Draw the condensed structural formula of the acetal formed by adding CH3OH to butanal. CH3CH2CH2CHO + CH3OH OCH3 CH3CH2CH2C H OCH3

General, Organic, and Biological Chemistry: Structures of Life, 5/e Karen C. Timberlake 2016 Pearson Education, Inc.

Recently Viewed Presentations

  • VOC sampling in San Antonio

    VOC sampling in San Antonio

    San Antonio ozoneTrends for April-October 2004-2018 ozone data. Estes, Air Quality Science, TCEQ Environmental Trade Fair 2019. Maximum daily eight-hour average (MDA8) ozone is the metric used to assess attainment of the ozone standard.
  • The biopsychosocial model

    The biopsychosocial model

    The biopsychosocial model (Engel, 1977) is a general model or approach that states that biological, psychological (which entails thoughts, emotions, and behaviors), and social factors (abbreviated "BPS") all play a significant role in human functioning in the context of disease...
  • Vocabulary - Mrs. Clifford's English Class

    Vocabulary - Mrs. Clifford's English Class

    Synonym- incongruous. ironic-(adjective) amusing or unusual because something strange or unexpected happens . The musty smell in the attic probably came from all of the socks we have been saving. Synonym-moldy. musty-(adjective) stale ...
  • i t s good and good for you

    i t s good and good for you

    Segmented pricing. is used when a company sells a product at two or more prices even though the difference is not based on cost. Price-Adjustment Strategies. To be effective: Market must be segmentable. Segments must show different degrees of demand.
  • Presentazione di PowerPoint - Media Salles

    Presentazione di PowerPoint - Media Salles

    European film promotion, Exhibitor training courses, Information. MEDIA Salles at the DC Independent Film Festival "Cultural Diversity & Digital Distribution in the Media" Mot
  • Facilites Services Summer Projects Update

    Facilites Services Summer Projects Update

    Rich Hall for School of Business & OBCR. OBCR to Relocate to Downtown Location (7/16) Business to Repurpose and Occupy Vacated Space (8/16) Hewitt Union (Hall) for Communications & Cont. Ed/Ext. Learning. Marano Campus Center for Cont. Ed/Ext. Learning. ADA...
  • Regulatory Modernization - Good for you. Good for Canada.

    Regulatory Modernization - Good for you. Good for Canada.

    Consumer Packaging and Labelling Act (1) Canada Agricultural Products Act (10) Applies to dairy, egg, fresh fruitand vegetables, maple and honey products marketed through import, export and interprovincial trade … With a single set of food inspection regulations that apply...
  • Your hospital room can make you sick! How

    Your hospital room can make you sick! How

    There is no direct correlation between RLU and microbial contamination, but "hygiene fails" determined by aerobic colony count and ATP do correlate1,2. Improve existing procedures. Fluorescent markers. Fluorescent material in the form of gel, powder or lotion can be applied...